Taperssection.com
Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: fivefishdiy on June 06, 2008, 10:59:45 PM
-
UPDATE: October 2008
This is the latest photo of the TS-2 Preamp prototype.
(http://farm4.static.flickr.com/3046/2897191138_414449d591_o.jpg)
Thanks to all the tapers that offered their suggestions, feedback and support!
The 1st batch of units are currently in production.... Serial #003 to #010.
ORIGINAL THREAD FOLLOWS
---------------------------------
Hello all. I make mic preamp kits for the homestudio/recording studio crowd. Usually, they're racked in a 1u case, with AC power and everything.
About 6 months ago, I started making a wallwart/battery powered preamp version, and finally just finished it a few days ago. A customer who's been following my progress emailed me and said this new pre may be a good fit for the "tapers crowd." I said "Huh?" and he explained what tapers are all about... apparently, he's into it and directed me to this site. I browsed around this site and this looks like a cool place to be.
Well, I have to say I didn't design this for compactness, because my original intent was this will be used in a studio. Anyways, I'm looking for feedback on what features are useful for tapers? (Size, battery power life, what else?) Maybe I can come up with something or modify this existing pre.
Some pics.
(http://farm4.static.flickr.com/3178/2552535381_11d9d51ec4_o.jpg)
(http://farm4.static.flickr.com/3052/2553226485_f214d2df4f_o.jpg)
Brief list of features:
Gain 6dB to 72dB gain
XLR input
XLR output
48V Phantom power switch (yes, it's really 48 Volts)
Soft start phantom power (no thuds when switching ON or OFF)
DC Servo
Balanced driver stage (can drive 600 ohm loads at long distances)
Powered by 12VDC wall wart (or battery)
From my testing... will work down to 6Volts, with phantom power falling down to about 36V with a 6VDC power input)
Here's an audio sample of the noise level... powered by a 12VDC wall wart, gain set to +72dB, volume at max, input XLR terminated with 150-ohm (to simulate a mic connected).
http://www.fivefishstudios.com/audio/SC1Solo-NoiseTest.mp3
MODS:
If this post is out of line or needs to be moved somewhere, I apologize.
I'm not selling these yet, as I'm not ready... this is just a prototype. Right now just looking for input and suggestions for features tapers would like to see.
Thanks!
-
:::clappping:::: :D
nice!
suggestions.. consider having unbalanced outputs, the ability for it to be run at 6-9volt max, and recess the knobs..
Im sure there will be more posts on this thread with further input Im sure.. enjoy the tapers section! ::tip cap::
-
Welcome to the board!
Very cool. If you are open to suggestions here are some from a taper perspective....just my opinion.
2 channel and or four channel versions
in a as small as possible metal case say 9"x7"x2" say brushed AL. or black AL.
first Variable knob for +or- 10 db
second indented knob in 10db increments from 6 to 76DB give or take
Runs on anything from 6volt to 12 volt
XLR input switchable line level to mic level
XLR outputs and RCA outputs.
Good LED metering.
Recessed front panel so knobs aren't acidently bumped
power switch on the front panel not the back
ability to turn phantom power on or off for dynamic mics or ribbons
and very low noise floor at maximum gain.......
Oh yes a fair price.....it can't break the bank.....tapers aren't rich but will spend for a good reliable product.
Anyone else want to add?
T+ for your project
if its good it will be the rage of the board! There is always room for more pre's
:realhappy:
Peace OOK
-
Thanks for the welcome and comments. I appreciate it very much!
Great suggestions, some that I haven't even thought of. Keep 'em coming.
BTW, this mic preamp design works with dynamic mics, condenser mics, FET condernser mics, tube mics and ribbon mics. No problem with gain settings or operation on any of them. (Check out MIX magazine May 2008 issue, this mic pre design was used in the gear review of a Peluso vs. Neumann mic.)
2 channel and or four channel versions
I think my PSU can handle that (2 ch). The current consumption of the mic preamp is only +/-17mA. (And 5mA of that is being used by the LED phantom power lamp, otherwise it's only +/-12mA)...
and YES, it runs internally on +/- split rail voltages. About 30V+ peak to peak voltage. Plus TRUE +48V for the phantom power.
in a as small as possible metal case say 9"x7"x2" say brushed AL. or black AL.
Noted. ... The case I'll be using is 6" x 4" x 1.5" and an option for 6" x 4" x 2.5"... single channel, extruded aluminum (not plastic), with anodized aluminum front and rear panel.
first Variable knob for +or- 10 db
I'm using a high-quality Bourns sealed potentiometer, conductive plastic... (will not get dusty, scratchy or worn out like carbon pots). It functions as a "trim/volume knob"... from cutoff to 0dB (i.e. no trim).
second indented knob in 10db increments from 6 to 76DB give or take
I'm using a high-quality sealed Grayhill 12-step, 1-deck selector switch. Gain adjustment is 6dB increment in 12 steps, from +6dB to +72db gain (balanced out). If unbalanced output, it will be from 0dB to 66dB gain.
Runs on anything from 6volt to 12 volt
Check. Done.
XLR input switchable line level to mic level
The current mic inputs can be used as line level inputs. Just set the gain switch down to 6dB.
XLR outputs and RCA outputs.
I think this is doable. Just need another jack. My balanced line driver stage behaves well with single-ended loads.
Good LED metering.
What is the definition of "good"?
I have a separate VU meter kit, but it only has 5 LEDs. Will run from 4V to 24VDC input (has on-board regulator).
(http://farm3.static.flickr.com/2172/2221808528_ddbe64a6b1.jpg?v=0)
if an LED VU is required, the 2.5" case height is probably needed.
Recessed front panel so knobs aren't acidently bumped
Good idea. I think this is more on the chassis/case construction... so need something to "guard" the knobs from being adjusted accidentally. I have to think about this one.
power switch on the front panel not the back
Hmmm... I don't have this. Need to add a power switch.
ability to turn phantom power on or off for dynamic mics or ribbons
Done... and my phantom power is a soft start. The 48Volts is ramped up gradually from 0V to 48V over a span of few seconds. So there is no big THUD when you turn on/off phantom power. Same thing when you turn it OFF, no big THUD... it's decayed down from 48V to 0V.
and very low noise floor at maximum gain.......
Is this good enough? http://www.fivefishstudios.com/audio/SC1Solo-NoiseTest.mp3
Oh yes a fair price.....it can't break the bank.....tapers aren't rich but will spend for a good reliable product.
I think the most common pre is the SoundDevices pre for tapers, is that right? Or do most go the DIY approach?
I don't have any pricing on this yet... still need to get quotes for extruded aluminum case with anodized front and rear panel.
QUESTION:
Is needing an external battery pack a big deal or a deal breaker? I don't have room for an internal battery. Hmmmm....
At the moment, this just a single channel mic preamp. In the future I'll be converting this to SMD and cut the size further in half, or cram 2 channels on the same board. But that's a far future.
Thanks for the comments.
-
This all looks great!
Possibly consider locking power input option for the field tapers. External batteries are ok, many here run 9 volt li-ion external DVD player batteries.
One case with dual pre's is what many wind up with, we are MOSTLY stereo tapers some 4 channel though.
Integral (to case) metering is a must, 5 led at a minimum as those of us running 16 bits need to run HOT! The more fine grained the metering , the better.
Thanks for your interest in our input.
Joe
-
Good LED metering.
What is the definition of "good"?
I have a separate VU meter kit, but it only has 5 LEDs. Will run from 4V to 24VDC input (has on-board regulator).
(http://farm3.static.flickr.com/2172/2221808528_ddbe64a6b1.jpg?v=0)
if an LED VU is required, the 2.5" case height is probably needed.
well, my opinion of "good metering" would be something like a light for signal, maybe lights at -30, -20, -12, and then a lot more details between -12 and 0, maybe a light at -9, -6, -3, -1, and an "over" light. Of course, that's my idea of good metering for digital levels. In this case, it's not an A/D converter, and generally speaking, I think we'd want to hit the clipping point of whatever A/D we're using (either external on the onboard A/D of our decks) before overloading the pre-amp. So now that I think about it, the metering on the pre-amp doesn't have to be as detailed, because the digital levels wouldn't necessarily correspond, depending on the sensitivity of whatever A/D we are using.
and speaking of how well your pre-amp will work with different A/D's and decks, it would be very helpful to know the maximum output level (in dBu) when the pre-amp is pushed to the limit (i.e. when it overloads). That way we all can know how hot to run the pre-amp based on whatever gear we've got downstream, and we can calibrate our other equipment most effectively.
Recessed front panel so knobs aren't acidently bumped
Good idea. I think this is more on the chassis/case construction... so need something to "guard" the knobs from being adjusted accidentally. I have to think about this one.
check out the Grace Design V2 and V3's for really good recessed switches.
Oh yes a fair price.....it can't break the bank.....tapers aren't rich but will spend for a good reliable product.
I think the most common pre is the SoundDevices pre for tapers, is that right? Or do most go the DIY approach?
I don't have any pricing on this yet... still need to get quotes for extruded aluminum case with anodized front and rear panel.
some people use sound devices pre-amps. they are small and nice pre-amps. but there are many pre-amps that people like to use. The Grace Design V2 and V3's are very popular, there are the Oade m148 and m248 pre-amps, the Neve Portico 5012, the Sonosax SX-M2, Aeta PSP-2 and PSP-3, Aerco MP-2, church audio pre-amps, etc, etc... I'm sure that there are many more as well, but this list is just off the top of my head for some more popular ones.
QUESTION:
Is needing an external battery pack a big deal or a deal breaker? I don't have room for an internal battery. Hmmmm....
some people prefer internal batteries. But for many people, external batteries is no problem.
At the moment, this just a single channel mic preamp. In the future I'll be converting this to SMD and cut the size further in half, or cram 2 channels on the same board. But that's a far future.
honestly, I don't think there will be much interest with just a single-channel pre-amp. The vast majority of people here record 2 channels, and some people have made the jump to 4 (with the advent of affordable, small, 4-channel recorders). But really, I think the vast majority of people wouldn't bother with two single-channel pre-amps.
Thanks for your interrest in our little community here. It's always great to have more options for gear, and to have the designers here in the community and listen to our wants and needs.
- Jason
-
it would be very helpful to know the maximum output level (in dBu) when the pre-amp is pushed to the limit (i.e. when it overloads).
The mic pre can do +22dBu, then it goes to the balanced line driver which adds another +6db gain. The balanced line driver max output level is rated +27dBu.
One case with dual pre's is what many wind up with, we are MOSTLY stereo tapers some 4 channel though.
honestly, I don't think there will be much interest with just a single-channel pre-amp. The vast majority of people here record 2 channels, and some people have made the jump to 4 (with the advent of affordable, small, 4-channel recorders). But really, I think the vast majority of people wouldn't bother with two single-channel pre-amps.
Wow! It should have been obvious but it didn't hit me till now. It needs to be 2 channels, AT LEAST, for tapers use. You're right! :-[
The above pre was originally designed for the recording/home studio, where only one instrument is recorded at a time during tracking... i.e. designed for a different purpose.
I don't think this particular layout will be well suited as a tapers preamp right now.
To do this properly and make it a real tapers preamp, I think I need to start from scratch. Use a wide but shallow case, new layout, put 2 (or 4) channels side by side, integrate the VU meters, add a clip indicator, maybe add a high-pass/low-cut filter, add an unbalanced out, design it really small and compact, add room for battery (if possible), etc. What do you think?
Thanks for all your feedback. It's invaluable.... time to go back on the drawing board and really design a proper tapers preamp.
Oh well, I thought I can adapt the above preamp for tapers use, but now I can see it's almost there but really it's not, still a long ways to go. Tapers have a different set of requirements.
-
Tapers are a very opinionated bunch. You can start holy wars on this stuff, and the various features, and the subtle flavors. Some of the most popular preamps for tapers are below. Look at those features and you will see where people are coming from. The V3 has steps and trim pots, the others have 0-100% knobs. Some people like this one, some like that one.
- the Grace Designs V3 (which contains an A/D, but has analog out too) http://www.gracedesign.com/products/V3/V3frame.htm
- the Apogee Mini-MP (analog in and out) http://www.apogeedigital.com/products/minimp.php
- Sound Devices Mix-Pre http://www.sounddevices.com/products/mx2master.htm
Personally, I think it's really important to have good level meters on the pre if it includes an A/D > bitbucket. If it simply provides boost, and I'm determining the final levels on another box with it's A/D (my R4 or R-09), I'm going to be watching the meters on the box with the A/D even if they suck, so in that case, I don't care if the pre has meters at all. YMMV.
Seriously, if you want to consider entering this market, you should package one up and loan it out to responsible people who can run it, and get some tapes up on the "Live Music Archive" at www.archive.org. The world is full of great preamps, but we don't touch most of them, because no one wants to be the first one to drop some money on something he can't sell later if he doesn't like it. Even if you stuff two of those boards into one box and run it, people may find out it runs sweet, or that it's way too bright, or some other descriptor, and then you can decide if you should start to think about a 2 channel box, or just forget about us altogether.
-
awesome! thanks for your interest and best of luck to you.
Look forward to some samples ;D
-
it would be very helpful to know the maximum output level (in dBu) when the pre-amp is pushed to the limit (i.e. when it overloads).
The mic pre can do +22dBu, then it goes to the balanced line driver which adds another +6db gain. The balanced line driver max output level is rated +27dBu.
One case with dual pre's is what many wind up with, we are MOSTLY stereo tapers some 4 channel though.
honestly, I don't think there will be much interest with just a single-channel pre-amp. The vast majority of people here record 2 channels, and some people have made the jump to 4 (with the advent of affordable, small, 4-channel recorders). But really, I think the vast majority of people wouldn't bother with two single-channel pre-amps.
Wow! It should have been obvious but it didn't hit me till now. It needs to be 2 channels, AT LEAST, for tapers use. You're right! :-[
The above pre was originally designed for the recording/home studio, where only one instrument is recorded at a time during tracking... i.e. designed for a different purpose.
I don't think this particular layout will be well suited as a tapers preamp right now.
To do this properly and make it a real tapers preamp, I think I need to start from scratch. Use a wide but shallow case, new layout, put 2 (or 4) channels side by side, integrate the VU meters, add a clip indicator, maybe add a high-pass/low-cut filter, add an unbalanced out, design it really small and compact, add room for battery (if possible), etc. What do you think?
Thanks for all your feedback. It's invaluable.... time to go back on the drawing board and really design a proper tapers preamp.
Oh well, I thought I can adapt the above preamp for tapers use, but now I can see it's almost there but really it's not, still a long ways to go. Tapers have a different set of requirements.
Nice job! I like the simplicity of this, just based on THAT/INA chips. I also like the battery power. Make it run with a variable input voltage 6-12V and you're golden. Oh yeah, make sure it will not fry if polarity reversed :).
Of course to fit the taper crowd you'll want a rugged case, and Neutrik (sp?) combined XLR/TRS connectors, and probably a pad, and a line/mic switch.
Other things (I think already mentioned) are locking and/or recessed switches, especially for phantom power.
Finally, remember the competition. SD mixpre/ Shure FP24 (transformer based preamps) are approx $500, so you'll have to come in at or less than this target price.
Richard
-
At the moment, this just a single channel mic preamp. In the future I'll be converting this to SMD and cut the size further in half, or cram 2 channels on the same board. But that's a far future.
Thanks for the comments.
For what we do as tapers it gotta be atleast 2 channel. Carrying one pre is much better that carrying 2 pres unless it is absolute audio nirvana most people will pass this up if its a single channel.
As far as metering I like this suggestion:
well, my opinion of "good metering" would be something like a light for signal, maybe lights at -30, -20, -12, and then a lot more details between -12 and 0, maybe a light at -9, -6, -3, -1, and an "over" light.
I am really looking forward to see what you come up with. What is the measurement on the noise floor?
As far as price IF you are talking strictly a two channel pre without an AD section, somewhere between 500 to 1000$ is what I would consider reasonable. This goes without saying, but I will say it anyway just make sure your using the best possible parts for the money.
I like the comment: You can start holy wars on this stuff, and the various features, and the subtle flavors. This is so true. There are a lot of people on this board who will open the box to peek inside at the quality of your components. I personally wouldnt know the difference. I go by what sounds good to me, its so subjective.
Some of the mics we tapers use are:
ADK TLs
AKG 391
AKG 451
AKG 480
AKG 414
AT 3031
AT3032
AT4041
AT 853
Averson
Beyerdynamic 930
Bussman Audio
DPA 4011
DPA 402-1-2-3
Earthworks
Joesphons
MBHO 603 or 648
Microtech Geffel
Neumann 140
Neumann 184
Oktava
Peluso
Rodes
Schoeps cmc6 mk?
Sennheiser
Studio Projects
THE audio
Violet Designs
I think I hit them all give or take............... 8)
Peace OOK
-
you should package one up and loan it out to responsible people who can run it, and get some tapes up on the "Live Music Archive" at www.archive.org.
Great idea! Well, I'm new here... so who are the responsible people here? ;D ;D
Okay, I'll put this single channel prototype in a case, loan it to some trusted people to give me feedback, and we'll see how it goes.
BTW, this is NOT a new or untested preamp design... it's been in use in home and commercial studios around the world... been selling them as kits for a year now.
What's new here is the "battery-powered/12VDC" powering option and that's when a customer told me about tapers and pointed me to this website.
Even if you stuff two of those boards into one box and run it, people may find out it runs sweet, or that it's way too bright, or some other descriptor, and then you can decide if you should start to think about a 2 channel box, or just forget about us altogether.
I like "passionate users" about their craft. I think this will be fun and challenging. It will be cool if this design also gets accepted by people recording "in the field." Right now, I just have people "in the control room/booth" using it.
Just PM me if you're interested in BORROWING it to test. I don't have a bunch of prototypes to loan out (and remember, this is just single channel), so not all may get the first crack at it but eventually I'd like to give everyone the chance to use or listen to it. To make things simpler, I'd prefer just USA users for now, and user must be willing to give me feedback (good and bad), be able to give me audio samples, and also post audio samples on the board too.
ok.. time to get working putting this in a case.
Thanks all.
-
Just sticking my head in this thread, since this looks like a promising option.
Ok, I'll put in my two cents, though as already mentioned, you'll probably get a lot of opinions, many saying the opposite thing. My few thoughts:
Stick with 2ch. Folks wanting to do 4ch can get 2 of your preamps. I'm guessing that hitting a small niche market means getting as many customers as possible, so no sense making a 2ch version and a 4ch version.
Since I have a Grace V3, I really like the design of a stepped gain with a 0-10db trim. I kindof think that the 10db steps makes more sense than the 6db steps if you already have 10db trim, but that is no big deal. If you can design it so you don't get a spike or pop when you step up the gain one step, that is great, since sometimes tapers will need to make this change while recording.
I agree with smokinjoe -- meters on a preamp aren't that important, I'll be watching the meters on my recorder or my AD. You can probably get by with 6 LEDs -- 2channels with -24db or -18db to show signal present, then -12db or -9db, then -3db or -2db.
If you make it deep, say more than 7-8", make it narrow and put the XLR connectors on the side. Or make it wider and shallower and put the XLR connectors on the back.
Batteries -- internal is def nice, but perhaps not required. I don't know if you get into problems with UL listing or whatever if you put batteries in, esp something like li-ion or li-poly. 12v isn't bad, but full 48v phantom with 7.2-9v is nicer since those batteries are a bit easier to find. If you need 12+ volts, it might be nice to use the li-poly 9v (500mah) or NiMH 9v (300mah) -- see thomas-distributing.com. If we could get this type of battery and just put 2 of them inside, with your low power requirements, that might enable runtimes of 6+ hours and be easily rechargeable.
Thanks for thinking about this market!!!
-
Thanks for the input. Keep 'em coming. I'm starting to get that "butterfly" feelings in my stomach when a bunch of ideas are starting to fit together like a jig-saw puzzle. I guess it's called excitement, HA! :)
12v isn't bad, but full 48v phantom with 7.2-9v is nicer since those batteries are a bit easier to find.
I checked my notebook, and yes, we can still get 48Volts from a 6VDC input. The split rail power supply for the chips though went down, but still +/-2.5V above the min. voltage required by the chips. So it still works. The "ideal" is 9VDC input... we get the 48V and the split supply voltage drop to power the chips isn't so bad.
I've drawn a preliminary sketch of what I want the "SC-1 Tapers Edition" preamp to be. I'll start laying them out on CAD towards the end of this week.
Anyways, I did some more testing tonight on my proto... and here are some photos. (I love photos :)
Testing... my single channel pre prototype. Phantom power ON, with the LED indicator lights on.
(http://farm4.static.flickr.com/3168/2563699592_e89f3b6016.jpg)
from a 12VDC input, let's measure the phantom power voltage.
(http://farm4.static.flickr.com/3137/2562874317_fdf6e9e846.jpg)
Hmmm 47.94 Volts... Close enough... if I could have adjusted the trimmers for a more exact 48.0 Volts, but phantom power is not picky. This is good enough for testing.
Hook up scope and try to measure the ripple on the 48V line.
(http://farm4.static.flickr.com/3006/2563699540_518ee431ea.jpg)
Hard to see... but the camera's shutter speed captured some signs of ripple. The scope is set to 50millivolts per vertical division.
Let's magnify it... set scope to 20mV per division.
(http://farm4.static.flickr.com/3010/2563699426_f849df035d.jpg)
Okay, now we can see some ripple caused by my switching PSU. According to the scope, the measured peak-to-peak ripple is 12 mV (or 0.012 Volts peak-to-peak). In RMS, that's 0.004Vrms.
It took me about 6mos. (working on and off) to fine-tune my converter PSU design for no RFI, buzzing interference, and get the ripple to where I like.
Photo of an earlier prototype PSU... (this one needs to be at least 3 inches away from the preamp XLR inputs for it not to cause interference... so it's no good for tight spaces where everything is crammed together in a portable case... it's fine though for a 1u Rack in a studio.) Shown is the same preamp design with input and output transformers, -20dB Pad, polarity reverse and a true balanced Active DI input for electric guitars/bass.
(http://farm4.static.flickr.com/3068/2352224005_5dc492842c.jpg)
-
Is that a Jensen transformer on the bottom pic to the left?
Oh yea welcome aboard!
-
My only question: how does it sound? I would hope to hell it is a clean, neutral pre-amp. The other bells and whistles are nice, but it just has to sound good.
Cheers
-
Is that a Jensen transformer on the bottom pic to the left?
Close... it's a Cinemag. Same "DNA" though :)
My only question: how does it sound? I would hope to hell it is a clean, neutral pre-amp. The other bells and whistles are nice, but it just has to sound good.
I'd like to say it is very clean and sounds great. But don't take my word for it. Here are some customer comments:
http://fivefishstudios.com/index.php?option=com_content&task=view&id=16&Itemid=46
And some mention in MIX magazine....
(http://www.fivefishstudios.com/images/MIX-May2008.jpg)
MIX Magazine, May 2008
I got some free publicity in MIX magazine in last month's May 2008 issue. The article is a review/shootout between a Peluso and vintage Telefunken microphones by Barry Rudolph, LA Engineer and MIX gear reviewer. He chose my preamp to test both these expensive microphones. i.e. Peluso 47SE mic ($1966)
Here's the link to the mic article... http://mixonline.com/gear/reviews/audio_peluso_se_tube
Another MIX mag gear review of IK Multimedia ARC software ... http://www.barryrudolph.com/mix/arc.html
SC-1 mic pre used too.
I tried both my RTZ Audio microphone pre-amp with transformers and my hand-built Five Fish Studios SC-1 direct-coupled unit. Apparently both were flat enough--I could discern no difference in the results with either pre-amp.
The RTZ is an awesome preamp... costs $1595. I feel good that my lowly SC-1 pre could hold up on it's own. :)
-
Today, I worked on the case. This is my current case for the prototype. This will NOT be the case used for the "Tapers Edition" preamp. Instead, it will be wider to accomodate 2 channels and 4 full-size XLR jacks, but shorter in height.
For now, I just want to get this prototype in a case.
(http://farm4.static.flickr.com/3040/2566269795_126cd2a615.jpg)
The case is extruded aluminum with PCB guiderails. It has good shielding characteristics. In addition, I add some support bolts to the PCB. I want to make sure the PCB is securely fastened to the case.
I laid out the parts and dimensions, and used it to generate the necessary Gcode files for my CNC machine. Went down to the garage and start miling. In a minute or two, it's done.
(http://farm4.static.flickr.com/3157/2567093700_cf376b6b19.jpg)
Test fit... and all the holes align perfectly.
(http://farm4.static.flickr.com/3142/2566269883_5be8d37e22.jpg)
Attach the nuts, looks good.
(http://farm4.static.flickr.com/3122/2567093810_f54ee663cb.jpg)
Start mounting the VU meter, attaching the XLR jacks, and knobs.
Rear view of the XLR jacks... perfect holes.
(http://farm4.static.flickr.com/3105/2566259781_1274a345c6.jpg)
And it's done. Single channel prototype.
(http://farm4.static.flickr.com/3264/2566246029_d44d2f97c0.jpg)
I'll play with this for a few days, just to make sure everything is alright. Then, I'll loan this single-channel pre to you guys. If I get good feedback from this, I'll proceed forward and make the 2-ch version with all the doodads (i.e. features) you guys requested.
-
i think a lot of people would be happy if they had the lundahl LL7903 on he input ;D
-
2 channel here we come!! :headphones: ed edit: is there a name u r considering?
-
That looks sweet!
-
is there a name u r considering?
Right now, I'm just calling it my "SC-1 Tapers Edition" preamp.... to distinguish it from my SC-1 kit, and my SC-1 Solo. (SC are the initials of a recording related website where this preamp was originally conceived back in Feb 2007 - StudioCentral).
Maybe it should be called "TS-1 Tapers Edition" since it will be born here...
Any suggestions?
-
One suggestion. Most tapers have their gear in Portabrace style cases, or camera cases where the recorder/pre is sitting down in the bag on it's tail or back end. The Sound Devices Mixers such as the MixPre and 302 have nothing on the tail or back end as far as connectors. All connectors are side accessable, so there is no gravity strain on the connectors such as the Grace and Apogee units face. When you build a 2 channel version, you would really get great response if you have the input/output connectors on the ends, but the control surfaces on the side facing out. Again, take a look at the Sound Devices and Grace units to see the form factor I am speaking of. Great work otherwise !!!
+T
-
is there a name u r considering?
Right now, I'm just calling it my "SC-1 Tapers Edition" preamp.... to distinguish it from my SC-1 kit, and my SC-1 Solo. (SC are the initials of a recording related website where this preamp was originally conceived back in Feb 2007 - StudioCentral).
Maybe it should be called "TS-1 Tapers Edition" since it will be born here...
Any suggestions?
Why not simply the SC-2 Stereo Pre-amp?
-
Some possible names:
SC-2
TSP-2 , Tapers Section Pre
The Little Black Box
Genesis 2, You know a new begining in dirrection for your preamps.
TAPT-2, stands for "Tapers Are Professional Too"
Peace OOK
-
Any idea of what the price point will be?
~Clint
-
Are you suggesting we call it Clint? ;D I kind prefer "The Pickle Weasel"
Damn...that thing looks like a Jenny Craig'd 148! If it sounds that good, we're all in for it! Have you even THOUGHT about what you might charge per unit?
-
Very cool news. Good job!
-
Thanks for the messages and replies. (Weird... somehow, the forum stopped sending me email notifications... I'm not getting them anymore. )
DATBRAD
Thanks for that tip. I've been looking at similar kind of cases made of aluminum with swing out handles, but it cost $100+! And that's without any machining yet, or silkscreen/engraving. I think I may have thought of a McGyver solution using a stock part item with some extra machining work, but I'lll need a few more days to think about it... and "sacrifice" a $50 case for this experiment.
OOK
TSP-2 , Tapers Section Pre .... hmmm... TP-2? (T.P. .... might sound crappy), TS-2
I think I like the sound of "TS-2" ... TS-2 Tapers Preamp
IowaClint
Price point? Nothing definite yet. Too early to say.
But here's some thoughts... I sell my 2 channels of pre, plus PSU, plus Power Transformer for $275... but it's in DIY KIT form. I sell a ready-made 2-ch unit for $650. But it's housed in a 1u rack case with 110/220V PSU. So in this case, you'll get a ready-made 2-ch unit without the transformer and without a rack case... but still using some sort of portacase, but with other features added also. So whatever the final selling price, It's probably going to be somewhere in between.
Thanks all!
-
Integral (to case) metering is a must, 5 led at a minimum as those of us running 16 bits need to run HOT! The more fine grained the metering , the better.
Joe
Agreed if I can get a pair of solid coaxes out > a nice pair of system cables, we should be in busisness. Now what I can't fiure iut iszzzzzzzzComcast @ HDMI and I acan't connect threstereo. to the CD/Widesceen
ertc
-
I sell my 2 channels of pre, plus PSU, plus Power Transformer for $275... but it's in DIY KIT form. I sell a ready-made 2-ch unit for $650. But it's housed in a 1u rack case with 110/220V PSU.
I can get a Sound Devices for less??
T
-
Show us some pics of your ready made 2ch units you sell for $650. I might be interested.
I love the feedback and I hope to see something cool created from it.
+T
Cheers, Phil
-
Show us some pics of your ready made 2ch units
This is the 4-ch unit... the 2-ch unit will be the same, except you'd have (2) spare channels you can fill up later on.
1u rack, anodized aluminum front panel, 0.125" thick, CNC engraved and milled (not silkscreen, not paint that will chip or get worn out). The front plate screws are now hex head stainless steel (this photo is an early prototype that uses aluminum screws).
(http://farm3.static.flickr.com/2340/1912252870_a28e60da2e.jpg)
The guts...(early prototype case, only 8" deep... the new ones are 11" deep for more room.)
(http://farm3.static.flickr.com/2344/1908585545_0e9b133373.jpg)
So there you go... 4 channels in a 1u rack case. Can be wired for 110V or 220V.
I hope to see something cool created from it.
How about some audio clips?
http://www.fivefishstudios.com/audio/SC-1PreampDemo.mp3
Note: The above clip is "unmastered." But every instrument you hear on this song was recorded using only the SC-1 pre. Drums, bass, guitars, DI input... various mics used for each instrument... Shure, AKG, Sennheiser, Ovation, Audio-Technica, Cascade Ribbon, etc. If you want a detailed setup of what mic combo was used with what instrument, PM me. Written and performed by Jason Mallow. Recording courtesy of Farview Recording, Chicago, IL.
http://www.fivefishstudios.com/audio/SC1-LB-Vocals.mp3
And the pre used with vocals ... on a Neumann U67 mic. Also used on some instruments. Rough mix... you can hear various tracks being muted/unmuted in the mix. I was told the CD will be out later this year. Artist: Mylene Farmer. Recording courtesy of Laurent Boutonnat, France.
-
Also, Id RATHER have the transformers in our 2-chan version. ;)
-
thanks for thinking about us.
QFT. Those clips sound great. Nice and detailed. I look forward to hearing what it will do out in the field. +T Also the little things like engraved markings instead of painted or silkscreened...that's the kind of attention to detail I like.
-
If you want detail, go poke around his website. .pdf manuals for the diy kits, a forum with some nice pics (frequency response, o-scope traces, etc). I'm impressed and looking forward to the results once this evolves past the proptotype stage.
-
The DIY, pre-made, and taper prototype pres are all transformeless right?
Do you have plans to add any of those cinemags into any of your existing or future designs?
I would also be interested to hear your thoughts on the transformer debate. I also live in Nashville and want one of your 4ch units.
I'll have to come by and check one out, till then...........wondering if you have any more pics of the units? Really large ones with lotsa detail.
-
The DIY, pre-made, and taper prototype pres are all transformeless right?
Yes.
Do you have plans to add any of those cinemags into any of your existing or future designs?
I have plans this year for an A*P*I type-circuit preamp. So the trafos will be an inherent part of the main board there.
For the SC-1 kit, I have an ADD-ON kit that I call the IO-Module. As I said earlier, it adds an input transformer, output transformer, Active DI with true balanced outputs, -20dB pad, Polarity reverse and a Mic/Instrument select switch.
It's on a separate PCB because not everybody wants the trafo option. (Also expensive).
I would also be interested to hear your thoughts on the transformer debate. I also live in Nashville and want one of your 4ch units.
Debate? What debate? ;D
It's all subjective. Some like it, some not. Sometimes it's preferable for certain instruments/genre, sometimes you just want a clean and clear, accurate capture without any flavoring.
There are cheap trafos, and expensive trafos. But either way you look at it, trafos are *very* expensive compared to a single IC chip .
wondering if you have any more pics of the units? Really large ones with lotsa detail.
Here you go, the IO module...
(http://farm3.static.flickr.com/2006/2346070867_beab684c82_o.jpg)
Big guts... bigger version, showing the guts.
(http://farm3.static.flickr.com/2344/1908585545_0cad152bf8_o.jpg)
Bigger photo.
(http://www.fivefishstudios.com/ffimages/sc1kx4-01.jpg)
-
I see the Mini IO mentioned and priced on your page, but can't seem to find the info on the IO with transformers. They are all Cinemag right?
What would be the price of a two ch version with IO and DI in a case, and do you have the cases that fit all of these modules? Seems like you could use the 4ch case and set it up for two IO/Di and Pre to sit side by side.
I'll probably just have to come by and see it person, but I am intrigued after talking with a studio buddy here in town.... he is currently using one and loves it.
Nice work! Thanks for the info
-
They are all Cinemag right?
Yes.
two ch version with IO and DI in a case, and do you have the cases that fit all of these modules?
I'm working out on a solution right now for this problem. The IO-module and Mini-IO just came out a few weeks ago.
Seems like you could use the 4ch case and set it up for two IO/Di and Pre to sit side by side.
Yes, that's the plan. I already had some prototype faceplates made, and I'll receive them next month. We'll see how it goes. Thing is, I'm 3-4 mos. behind schedule on products I should already have put out. My real job gets in the way ;D
-
Okay tapers... the UPS man visited me today bringing along some gifts.
I ordered several cases a few days ago and so today I start playing with them. I think I found a winner. Big enough for 2 channels, but not too big. Very lightweight, good RF shielding. I'm really happy with this one.
I mocked up the front panel, put some aluminum bracket, and this is what we get.... what do you think?
I still have some real estate space on the front panel... could be used for 5-LED VU, or a Signal Present indicator, and a Peak/Clip indicator, and 48V phantom power indicator... I think we can also squeeze in a power lamp.
These are regular size push-button switches... the caps are RED, GRAY, WHITE (phantom, pad, and ? - any suggestions?) I may replace them with micro-miniature switches. Don't know for sure yet. Knob is for the Gain switch, 12-step detent, 6dB per step, 6dB to 72dB gain.
Photos:
Future (2) channel TS-2 Preamp, with full size XLR jacks at the rear. Size is 6" x 6" x 2".
(http://farm4.static.flickr.com/3281/2572411362_193fc5d48b_o.jpg)
Another angle...
(http://farm4.static.flickr.com/3194/2572411394_6764211fe2_o.jpg)
-
Pretty sweet. I like the simple rugged design. The VU meter is a good idea, along with phantom switch. I don't see a need for phase or pad switches at all, not for two track field stuff. No need to ever flip the phase if you set up in the right location. Can't see a reason to ever use a pad either. A HF filter option would be nice, since that's probably the only area that tapers will adjust their recording live, everything else should be done in post. Simple, clean, reliable. function over form.
EDIT: also would love to see a fine tune adjustment, such as the trim controls you have on your SC stuff. The 6db steps are perfect, with the addition of a trim knob.
-
I don't see a need for phase or pad switches at all, not for two track field stuff. No need to ever flip the phase if you set up in the right location. Can't see a reason to ever use a pad either. A HF filter option would be nice, since that's probably the only area that tapers will adjust their recording live, everything else should be done in post. Simple, clean, reliable. function over form.
I think a pad is a great idea, even more-so than a high-pass. You can cut bass in post, but you cant fix a clipped signal. A pad is a nice thing to have when using a pre as a front end for a board feed as well. It already fits in that small form factor anyway. Add the 5 led metering and your golden. Great looking work!
-
What about the TRIM? I took it out because it takes a big amount of real estate space on the panel.
Of course, the other option is not using a step gain switch and just using a pot for the gain control... but that's kinda dorky... you can't select the exact gain you want it.... it will save a lot of money though since a pot is cheaper than the 12-step selector switch. But I really like the 12-step switch.
Maybe a very small trim pot shaft? Is that attractive? or useless?
High pass... what's the cutoff freq? 80Hz, 160Hz? Lower?
I think the pad will stay... it will be useful for using the pre as a line preamp.
Polarity switch... I may bring this to the rear panel, beside the output XLR... so it's not taking up space on the front. Using a very tiny pushbutton switch.
Hmmm.. in that case, the Pad switch can also be brought to the rear panel... beside the input XLR. That makes more sense.
So that leaves the HP filter and the 48V switch on the front panel, plus the gain selector and the trim knob... and the VU meters.
Should the power switch be at the front panel? Or will it be okay in the rear panel?
Hey what about LIGHTS? So you can see what you're doing in the dark? Hmmm.. But that would eat into battery life. Or do you guys just bring flashlights/cellphone/blackberry/ipod?
-
VU Meter would be cool, but not totally necessary with most of the recording devices we have.
48V Absolutely
Pad Great Idea
I, personally, could care less about a pass filter.
I must say...I'm interested in hearing how this sounds. Something so small could do wonders for downsizing mid-range rig.
-
I just don't see a need for a pad on a preamp. You could just bypass the preamp altogether if the signal is so hot that it requires a pad. Seems ridiculous to amplify a signal that will require a pad. That would only come into use in line level amplification, which I don't see this being used for very often. I'm not opposed to a pad by any means, just don't think I have ever needed one on a preamp to record a live show. I would just bypass the pre and go direct to recorder and use a pad there if needed.
Putting any push-type buttons on the back might present a problem. Anything that can be accidentally pressed can and will be an issue with tapers.
I'm fine with or witout HPF. I like the idea of no trim knobs and pots for the gain knobs instead of steps. It's simpler and works just as well. Leaves more room for the Vu meter and more stuff on the front.
-
nice and simple, juts like I like it ;D I would rather have a transformer preamp personally tho ;D
-
Small suggestion: an unbalanced stereo mini-out or a pair of RCAs outs? For those of use planning on running a D50 or a R09.....
-
What about the TRIM? I took it out because it takes a big amount of real estate space on the panel.
Of course, the other option is not using a step gain switch and just using a pot for the gain control... but that's kinda dorky... you can't select the exact gain you want it.... it will save a lot of money though since a pot is cheaper than the 12-step selector switch. But I really like the 12-step switch.
Maybe a very small trim pot shaft? Is that attractive? or useless?
High pass... what's the cutoff freq? 80Hz, 160Hz? Lower?
I think the pad will stay... it will be useful for using the pre as a line preamp.
Polarity switch... I may bring this to the rear panel, beside the output XLR... so it's not taking up space on the front. Using a very tiny pushbutton switch.
Hmmm.. in that case, the Pad switch can also be brought to the rear panel... beside the input XLR. That makes more sense.
So that leaves the HP filter and the 48V switch on the front panel, plus the gain selector and the trim knob... and the VU meters.
Should the power switch be at the front panel? Or will it be okay in the rear panel?
Hey what about LIGHTS? So you can see what you're doing in the dark? Hmmm.. But that would eat into battery life. Or do you guys just bring flashlights/cellphone/blackberry/ipod?
For what we do there is no need for a phase switch.
A pad switch is nice but again not always needed.
I would prefer a variable gain as a posed to step gain. More control.
Hiss pass is nice but again I would rather fix it in post. You can't put back what isn't there..........
I would avoid putting any switches on the back panel if at all possible. Because Tapers carry their stuff in some kind of bag and the chances that a switch may flip increase when on the back panel. The worst part being not knowing it flipped until after the show. Unless you use some type of lock out swtich, like a toggle switch with the lock out that comes over top. The only thing that comes to mind is like something you see in a fighter jet. Dam I watch to many movies....lol
Peace OOK
-
Field taping require me to run from bag. No switches on back is safer.... As this is a vertical set up, I need "legs" to keep my UA-5's outputs from bearing the weight of the box itself....
-
Another vote for nothing on the back; anything not on the front panel I would prefer on the side. Anything on the back would require me to pull the equipment out of the bag to reach it and see which switch I was flipping. I would prefer to leave everything in the bag and my Kata Koala bag offers access to both sides.
HPF, have never used it; pads, I use the one on the mic if needed; trims, I find them useful when running mics>recorder which is what I've run for the past 8-10 months, probably more useful if staying with stepped gain rather than continuously variable pots. Phantom and power should both be on the front along with trims if used. Anything that's variable should be on the front, anything other than the power switch and phantom that is on/off can go on the side.
Only way to please everybody would be to make a custom box for everyone. I'm sure you don't have the time for that. Looks like it's time for me to brushup on my soldering skills, order a stereo kit and build my own custom SC-1Dualchnnel.
ymshouldv
Thanks for asking for our input.
-
Okay... nothing on the back, no switches or anything.
I will try drilling holes on the sides of the blue box above... see how difficult it will be. That's something that will have to be done manually as opposed to CNC. (I'm trying to avoid manual labor. ;D )
What do you guys think of this case? I can easily put drill holes and mount XLR jacks of all sorts on the sides (still manual drilling though) but it's made of plastic... not aluminum like the first kind. I guess I can tape EMI shield tape insides for good measure. It's also a little bigger than the blue case. But hopefully not much.
(http://farm4.static.flickr.com/3186/2572901509_85db2d74c8.jpg)
(http://farm4.static.flickr.com/3116/2572901565_497becb788.jpg?v=0)
(http://farm4.static.flickr.com/3040/2573724302_42fed2b5a1.jpg?v=0)
-
Okay... nothing on the back, no switches or anything.
I will try drilling holes on the sides of the blue box above... see how difficult it will be. That's something that will have to be done manually as opposed to CNC. (I'm trying to avoid manual labor. ;D )
What do you guys think of this case? I can easily put drill holes and mount XLR jacks of all sorts on the sides (still manual drilling though) but it's made of plastic... not aluminum like the first kind. I guess I can tape EMI shield tape insides for good measure. It's also a little bigger than the blue case. But hopefully not much.
(http://farm4.static.flickr.com/3186/2572901509_85db2d74c8.jpg)
(http://farm4.static.flickr.com/3116/2572901565_497becb788.jpg?v=0)
(http://farm4.static.flickr.com/3040/2573724302_42fed2b5a1.jpg?v=0)
dimension wize that box looks sweet! with some modifications (knob protection) you have a winner there I think..
-
For field use I would not buy a unit encased in plastic. Just my .02. YMMV though
-
I personally love that case. The ability to angle it up like that is great!
Most of the all-in-one recorders are all made of plastic and a large percentage of people here own those without complaint....
thumbs-up here...
-
Again you can't please everyone. I like the demisions of the case. Loose the handle though. As for the back no switch ect but xlr's are acceptable. But xlr's on the side are fine as well. I would prefer a metal case as aposed to plastic. I look at it this way, when building a quality pre why skimp on the case, metal all the way.
Peace OOK
-
On the HPF issue, there is a pretty big split in the taper camp on whether to use one it seems to me. I personally like having the option of HPF and use it fairly regularly, though not often. Maybe it depends on when you started taping. I started in the DAT days and wanted everything as good as I could make it right when I made the tape. Many folks now would just prefer to do HPFiltering in post with software.
Anyway, if you put one in, I'd recommend 80Hz, 6db/octave. You don't want a sharp rolloff of 12 or 18db like you might want for ENG or voice.
As to switches on the back, probably not ideal, but if they are small sliders in between XLR jacks and unlikely to get switched inadvertently, they should be ok if you need to do that for real estate purposes. But I'd only put say 48v phantom switches there. You wouldn't want power or HPF or whatever that you would want to have access to during the show you are taping, since as mentioned many will run their gear vertically in a field bag.
I run a Grace V3, and don't particularly find it problematic to have XLR inputs/outputs on the back. Again, different folks will have different preferences. To me, it is easy enough to right-angle XLR cables into the back. If you do have the XLR connectors on the back, make sure you leave enough room between them to have all right-angle (neutrik) XLR connectors on there. You can easily space them tight enough that regular straight XLR connectors will fit even though RA connectors won't fit, and that isn't good.
I'd prefer having the stepped gain with separate trim knobs like the Grace V2/V3 since I find that a great setup. I have gotten used to be able to really dial in my gain exactly (again getting back to my DAT days). I can't get over wanting to do that, but it does seem that at 24bits, having the gain roughly right (i.e., with stepped gain and no trim) should be easy enough to fix up in post using software. So maybe skipping the trim knobs should work out. I'd prefer stepped gain using resistor arrays over variable pots for the full gain range, since those always seem to get noisy over time or start drifting out of accuracy.
BTW, I vote for the blue case. Keep up the great work!!
-
Thanks for all the feedback. It's helping educate me...
Man, designing the circuit and PCB is the easy part. Picking the right case, and engineering everything to fit and work together is the hard part. (It always has...)
Using the blue case, I tried drilling XLR holes on the side. Surprisingly... it was easy to drill 15/16" holes. I used my trusty step drill. The problem is drilling the 1/8" mounting holes. They fall exactly on the curve ridge of the case... ever try drilling on the center of a convex surface? The result was misaligned holes and which makes the XLR jacks crooked, which involves more work straightening it out. I emailed the factory to see if they will do custom mods for me and have them drill these holes for me! If yes, that solves one problem.
It took me HOURS to do these holes... but I was also figuring things out and trying different things. Compare that to 2-3 minutes milling the rear panel with my CNC!
I'll probably create a drill jig/template with my CNC and use that jig when manually drilling the case, see if that makes the manual process faster and more accurate.
An option I'm thinking is doing 2 versions... and charging more for the XLRs on the side model to justify the added labor that's involve. The XLRs at the back will be priced cheaper.
As for the stepped gain + trim VS. pot control... if I'm going with the pot control, I need a special kind of pot with my circuit. I need what you call a Reverse Audio Log Taper. Not a Linear Taper, and not a Log taper, but a Reverse Log taper! It's a special order item and I asked my sales person to give me a quote for these special pots.
Personally, I still prefer the step gain + trim... but weighing on the cost compared to pot control, the pot control is attractive... but since the pot is a special order item (i.e. expensive), I may just use and go back to the original plan of gain + trim.
Okay, photos of the blue case with the XLRs mounted on the side.
(http://farm3.static.flickr.com/2084/2574734500_0781a07b5f.jpg)
(http://farm4.static.flickr.com/3116/2573911399_42eb89677b.jpg)
Again, the front panel layout is not finalized... still playing around with it.
-
ok, I take my comments back. After seeing these pictures, I am sold on the blue case! FWIW, I don't think the xlr's on the back are a problem and might be preferable for some...
-
I love the blue case.........6x6x2 perfect........
Boy I can't wait........to see the finished product.....I guess I need to start saving now.....
OOK
-
Very, very nice.
its great to see folks like yourself discover us,...and find excitement w/the target market.
bravo!
I'd throw down w/a set of features that I'd like...but you've got everything covered basically.
Now, here are the marketing aspects of our community. perhaps these points will dictate/drive functionality of said preamp.
as for a name, I say keep it what you have. maybe throw a "FV field version" in there.
:)
- we strive for sound quality. we like our preamps to be quick and clean. no noise. no commissions. Not to say we dont like our "flavor" too, but there are many preamps out there w/that.
- we like "in the bag friendly". recessed controls, side accessable cables, exteranal DC power that is easy to run off of Lithium Ion products (like DVD batteries for those portable players) that output 9-12v.
- 4 channel recording is a hot ticket right now. lots of people doing it, or wanting to.
- "dongle" cables to cut down on space. Instead of various I/Os and the room that the jacks require, think about a single 5pin output, either w/switchcraft mini's (ta5) or full sized 5pin XLRs. then you have various breakout cables which you can market or leave to the cable makers (we have several wonderful companies here on the list making custom cables). This way you can have balanced/unbalanced and any flavor of output from the preamp to recorder.
- as mentioned...lights are not all that relevant. one to show its "on". one to show that its "going to die" and one to show that its clipping, or close to it. Many people like to run their gear "hot". so a light at -2db would be perfect. Lets us know what the box is doing before sending a signal out to a recording deck.
- small, light, easily concealable.
- cost effective. put the investment into the internal parts and dont sweat the exterior.
Now, if you really want to get fancy and have a product that no-body else offers:
Many (and I mean many) people here run modular microphones with "active" cables. Think schoeps collette, Neumann KM100 series..etc.
build a preamp that can eliminate the need for the preamp body of these modular systems.
Something lemo style connectors for the Schoeps active cables and Neumann ka style older active cables.
There are only two boxes like this in existence.
1. the schoeps VMS (which will only work w/the schoeps mics, of course)
2. Sonosax "lemosax" version, no longer in production. This would take the schoeps and the neumanns, I believe.
We also have new modular kits w/active cable solutions in the pipeline from:
- Beyerdynamic
- VMlabs
- Peluso (cemc6 condensers)
and, the wish of all wishes..., build an active cable for the AKG c6x series caps that will work w/the c480 body *(or no body at all).
it doesn't exist (for all intents). one fella used to build them, but no longer.
-
Thanks Nick for the welcome and your inputs! Much appreciated.
- "dongle" cables to cut down on space. Instead of various I/Os and the room that the jacks require, think about a single 5pin output, either w/switchcraft mini's (ta5) or full sized 5pin XLRs. then you have various breakout cables which you can market or leave to the cable makers (we have several wonderful companies here on the list making custom cables). This way you can have balanced/unbalanced and any flavor of output from the preamp to recorder.
Okay... I investigated and this is doable. Will offer this as an option for the rear panel. Lemo style jacks and receptables, with BAYONET LOCKING connector. One cable for 2-ch BALANCED inputs, and one cable for 2-ch BALANCED outputs. (of course, the breakout cable can be wired for 2-ch unbalanced inputs and unbalanced outputs, or whatever combination thereof.)
Due to physical constraints on the receptable (i.e. maximum panel thickness), I will not be able to install it on the sides... but the backs will be fine.
So the different options are:
- Bayonet Jacks on the Back
- XLRs on the Back
- XLRs on the Sides
.... still don't know how to address the RCA outs or mini stereo (i.e. room on the rear panel)... but if you have the Bayonet jack, you can put whatever RCA or mini-stereo, 1/4" jack you want on the other end of the cable.
- as mentioned...lights are not all that relevant. one to show its "on". one to show that its "going to die"
Hmmm... haven't thought of the low-battery indicator. I'll see what I can do.
and one to show that its clipping, or close to it. Many people like to run their gear "hot". so a light at -2db would be perfect. Lets us know what the box is doing before sending a signal out to a recording deck.
[/quote]
I assume you mean -2dB Full Scale (i.e. digital)... and not -2dBVU (analog). Ok, a PRE-clip indicator...
build a preamp that can eliminate the need for the preamp body of these modular systems.
If this unit does well, I'll look into that as a future possibility.
build an active cable for the AKG c6x series caps that will work w/the c480 body *(or no body at all).
it doesn't exist (for all intents).
Sorry for my ignorance. What's an active cable? a mic Pre in the jack of the mic? on a cable?
-
very nice!! love the side xlr's. just keep the powering easy, and it will be a winner!! ed
-
Some thoughts on packaging:
If you use something like a 5-pin mini-XLR or LEMO jack on the back, make sure those connectors have matching cable ends that can be right-angle. That is, you can get a neutrik RA 5pin XLR, but you can't get right-angle mini-XLR cable ends, and I don't know about LEMO parts. At 6" deep, people using typical field bags will not have much room available for straight cable ends and will want RA.
If you want to stay with side connectors and the XLRs are hard to install on the case, you might think about using switchcraft mini-XLRs (Tini Q-G, TA-3F or TA-3M):
http://www.switchcraft.com/products/connectors-23.html
The TB3M panel mount connector might be able to fit on the side of your blue case without too much hassle. (http://www.newark.com/productimages/nio/standard/4079762.jpg)
Of course, you might want to get feedback on this, since mini-XLRs are used a bit on taping equipment, but aren't as standard as XLRs. So people buying your preamp with these will need new cables made.
The other thing I noticed is that the handles on the blue case take up a bit of real estate. You might want to consider leaving them off and freeing up this room for switches, etc. I'm not sure how folks would feel about not having this protection.
I also wasn't sure what the various switches you have on the mock up for the blue case. It might be possible to find some different switches that take up a lot less room. I'm thinking about mini toggle switches like on the Grace Lunatec V3 of the mini slider switches like on the side of the Sound Devices 722 (which also shows the TB3M mini-XLR outputs):
(http://sounddevices.com/images/products/722-lp-345.jpg)
This might leave enough room up front for more LEDs, or even an 1/8" mini output (so you could have XLR outputs on the side and the mini-out on the front).
-
Another vote for a lemo/binder version so I can run my Schoeps actives.
Here's some features I would like to see and in my opinion would make your box a stellar unit:
1. lemo/binder connections to power active caps
2. all connections on 1 side
3. power loop, I would love to send battery power to this unit and come out to my SD7XX without using a splitter.
4. in conjunction with #3, good clean powering at 6.8-7.6 volts
5. a 4 channel version
The sonosax SX-M2/LS2, while a nice little box fails (IMO) with the power requirements.
At 12 volts, there is not much headroom, it really wants 16-24 volts. But, it also sucks power quickly.
If you could offer a box that would run nice and clean at ~7V, power active caps and pass through power to a recorder, you will be miles ahead of everything else out there!!!
-
Todd, thanks for that tip! That is a great tip!
I'm ordering some mini Switchcraft jacks to see how big they are... their website doesn't give much info on the more important details like dimensions.
But looking at the pic... it *may* work... the only thing I find weird is their male jacks are circular, but the female jacks are not available in the same form factor (instead it comes with the square flange). Anyways, I'm ordering samples to investigate that further.
The cost though is 3X the normal XLR jack. We're talking $36 already just for the (4) mini jacks alone. Hmmm....
Okay, so we'll have the following ordering options...
a) XLRs on the back
b) mini-XLRs on the side
c) Lemo/Binder jacks on the back
the handles on the blue case take up a bit of real estate. You might want to consider leaving them off and freeing up this room for switches, etc.
I kinda like the look of the handles... leaving it off makes the unit look drab and exposed. But yes, they take up a lot of space....
There's the future possibility of making custom handles that will get attached using the existing 2 screws on each side of the front plate.
It might be possible to find some different switches that take up a lot less room.
Yes, those switches will get changed with a more smaller switch... 5mm diameter. These are just mockups to see how the box will typically look.
midside
I'm still not sure what's an active mic, so I don't think my lemo/binder jacks will work with those. I don't know... Does it require extra circuitry inside the preamp box for these active capsules to work? Are these Electret condenser mics? kinda like the Panasonics? Do they require other voltages other than 48V?
Do you have a website link explaining these kind of things?
QUESTION
Where does the DC Jack typically go? And do you use some sort of binding post to wrap the cord around it so the jack doesn't get pulled out? What kind of protection does your unit uses to prevent pullout of the DC plug?
-
the apogee units use a cord holder tightened by a screw.
(http://aes.harmony-central.com/115AES/Content/Apogee/PR/Mini-MP-rear-lg.jpg)
-
if there is room, xlr 4 pin for power. ed
-
Basically, Schoeps (as well as other manufacturers) have modular systems where different microphone capsules can be interchanged on the microphone bodies. Ideally, these capsules run on 62V while the bodies are supplied with the standard 48V. I don't technically know what it takes to properly power the capsules, but I do know that the circuit in the body is very small and looks simple enough.
Here's a link:
http://schoeps.de/E-2004/cmc.html
Other members here should be able to give you a schematic of the circuit in the mic body.
At near $1000 a body:
http://posthorn.com/S_cmc.html
you can see why a box that would let us bypass this would be desirable.
I'm positive that many members here would be very happy with this option!
OK people, chime in and back me up on this one....this is what we want....right?
-
OK people, chime in and back me up on this one....this is what we want....right?
Great option, but I think supporting modular caps directly from the preamp - without the mic bodies - is a very small niche. The Sonosax SX-M2/LS and /LS2 has been available for a long time (though not any longer, it seems) and will work with at least Schoeps MK-x caps and Neumann AK-xx caps (and maybe AKG CK-x caps? though I think the issue here is availability of the male threaded adapter to screw into the cap), yet not many people use them. And I don't think it's because of the Lemosax's power requirements. I think there's just not much demand; it's a very niche requirement. $0.02
-
Re: breakout cables.
If you can, please stay away from LEMO. These are hard to find, and expensive.
If you make power and/or mic and/or line i/o out of XLR or miniXLR, lots of the "cable guys" on this forum can build cables for different people's needs. This means you can focus on the box, and not worry about individuals' needs (various power supplies, right angle vs straight connectors, etc).
Another point, as others have shown, is copying ideas from existing units. For example, copying the standard 4-pin XLR power connector is a good idea. I'm not sure what units use this, but it seems to be popular, at least with the crowd here.
Finally, about the "actives". I would just focus on the preamp for now. Perhaps you can offer special options later, but if you build a great field-power preamp with more or less standard connectors, that gives you the most potential in sales.
Keep up the good work.
Richard
PS: Finally, you *might* want to offer kits once you get everything done. There are people, myself included :), who would love to just solder this thing up if you gave the case and all the parts.
-
4pin XLRs for power are nice, but it doesn't seem they are in use that much these days on field equipment, maybe either because lead-acid ecocharge batteries aren't used as much or because the 4pin connector takes up a lot of real estate.
Another possibility is a locking coaxial connector like the switchcraft s760k:
http://www.switchcraft.com/products/jack-146.html
Which means for your preamp you'd need something like:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=090-488
For cases, if you wanted to make a more custom size (like 8" wide and only 5 or 5.5" deep), maybe something like the 175DT option here would work:
http://www.enclosuresandcases.com/dtspecpage.html
(http://www.enclosuresandcases.com/images/175dt.gif)
This might allow a wider, shallower case that allows more real estate on the front and back for connectors, switches, and gain pots.
BTW, it seems that gear using the mini-XLR connectors use the male connector TB3M for both inputs and outputs.
-
Lookin' good man +T. ;D I'm with Todd on the 4pin XLR's. I know they are/were industry standard and all, but they seemed overly expensive and large. I did like the switchcraft locking jack that he links to above, ala my old MP-2.
-
Bluegrass
Thanks for that pic. <thumbs up!>
midside
I don't own any of those kind of mics or capsules, so it will be hard for me to design for them... impossible or no way for me to test it and play with it. Maybe sometime in the future... if I can figure it out. From the description on their website, it's either the mic circuitry that's been moved outside the mic case into the preamp box, or some sort of an Active DI circuit. So maybe I'll file this away and will look at it some more at a later time.
illconditioned
If you can, please stay away from LEMO. These are hard to find, and expensive.
Oh man, I thought Lemo and Binder are the same company. Yikes, LEMO is even more expensive than Binder.
If you make power and/or mic and/or line i/o out of XLR or miniXLR, lots of the "cable guys" on this forum can build cables for different people's needs.
The miniXLR is showing some promise... ordering some this afternoon and we'll see how it goes. If I can find a different kind of case that will allow easy machining (either by the factory or me in the garage with my CNC), then full-size XLR holes on the side will be a possibility.
Keep up the good work.
Thanks!
Todd R
Another possibility is a locking coaxial connector like the switchcraft s760k:
http://www.switchcraft.com/products/jack-146.html
Which means for your preamp you'd need something like:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=090-488
Perfecto Mundo! I like it. Price is reasonable, functionality high. <thumbs up> Thanks for the links!
For cases, if you wanted to make a more custom size (like 8" wide and only 5 or 5.5" deep), maybe something like the 175DT option here would work:
Schweeeeet! Now we're talking. The plain flat sides will make mounting of full size XLR holes easy... and the breakable box means I can even mill and machine all the panels in my garage CNC, instead of having the factory do it.
This case OPENS UP (pardon the pun) a lot of possibilities. I can stick every kind of jack on every panel on this thing!
Great find! Thanks for the link.
-
I would also like to suggest Hirose connectors, less expensive than Lemo, Binder, or Fischer. SD uses the small HR10 series for their recorders power inputs. This connector is very common in the broadcast camera world.
I notice that you live in the Brentwood area, I am in east Nashville and have a selection of Schoeps mics, capsules and cables if you would like to try them out.
David
drpro@sonusclarus"period"com
-
(http://www.audiodesignguide.com/DAC_final/photoLundahl.jpg)
-
Okay, so I drilled some holes on the front panel to install the brackets... I want to see how much available space I'll have left.
(http://farm4.static.flickr.com/3078/2577319605_65dc69f5d0.jpg)
Start laying out the PCB dimensions and cutouts, I'll use a double-sided PCB, and it will have (2) levels... a bigger "motherboard" and a small "switchboard" elevated on top. Then I realize, man, I have so much wasted space on the backend of the PCB. What can I put on there?
And then I had a flash of inspiration... check it out. See those (2) silver cans? ;D
XLRs on the back
(http://farm4.static.flickr.com/3144/2578152546_299d6298eb.jpg)
XLRs on the side
(http://farm4.static.flickr.com/3001/2578152568_7a7813d8b7.jpg)
The unit will have (2) DC jacks (see the 1st sketch)... a normal DC jack (for wall warts), and a Switchcraft locking DC jack. Both jacks can be used in parallel if needed... i.e. say you have 2 battery packs, and want to replace batteries without unplugging the first jack. The (2) jacks have different dimensions for the pins.. 2.5mm and 2.1mm.
And yup... I'll use a 12-step gain switch (6dB per step) AND a trim knob.
-
+t
-
+t
this thing looks nice. are those the full size xlr's in the "on the side" sketch? this is very exciting to watch you create from scratch.
-
(http://www.audiodesignguide.com/DAC_final/photoLundahl.jpg)
mmmmmmmmm....nice warm lundahl.......like hot chocolate on a snowy day.......OOK
-
Front panel monitor jack? That would. Need a level control.
Unbalanced out (1/8" stereo) on front panel?
With the main/daughter boards, is there still room on the front for the VU board? Could the mono VU switch between channels via switch and have signal (-24?) And pre peak (-3dB?) for Both channels? Otherwise VU should be stereo, right?
Thanks for taking suggestions!
Joe
-
+t
this thing looks nice. are those the full size xlr's in the "on the side" sketch? this is very exciting to watch you create from scratch.
Me too. I love watching this whole process. Best of luck with it...
Richard
-
halleyscomet8
On the photos, yes, those are full size XLRs. I'm still waiting for my order of mini-XLRs and may use them instead (as Option 2).
bugg100
>> Unbalanced out (1/8" stereo) on front panel?
Hmmmm... may be possible if I can find space for a PCB mount jack, probably... no promises.
>Front panel monitor jack that would need a level control.
Sorry, no more space for the knob/pot on the right side of the front panel.
With the main/daughter boards, is there still room on the front for the VU board? Could the mono VU switch between channels via switch and have signal (-24?) And pre peak (-3dB?) for Both channels? Otherwise VU should be stereo, right?
Hmmm.... that's a good idea. A 3-way switch, switch to the left to monitor VU for the left channel, switch to the right to monitor the right channel, and switch to the middle to turn off VU meter and save battery. And there's plenty of space on the dautherboard for that too...
I'll be able to answer this a definite YES or NO when I get the first prototype PCBs made, to see how tight it will be.
illconditioned and halleyscomet8
Thanks!
-
On the photos, yes, those are full size XLRs. I'm still waiting for my order of mini-XLRs and may use them instead (as Option 2).
Is there really any advantage of using mini-XLRs over regular XLRs? Space doesn't seem to be an issue on the back or the sides. Most people would probably prefer regular XLRs. Now if you wanted to really reduce the size of the box then I could see using mini-XLRs
Rick
-
I'll throw my .02 in
Keep it simple and keep the cost down.
XLRs IN and Out (Maybe 1/8 or RCAs out)
6db stepped gain (most of us use recorders that can fine tune the levels)
Simple UV levels (3 or 4 meters - 24db,12db, 6db and 3db)
Power Switch
Trim Knobs, 10db pad and Clip Indicators would be nice too :)
If it sounds good and its reasonably priced, people will buy it.
-
(http://www.audiodesignguide.com/DAC_final/photoLundahl.jpg)
Indeed...here's the inside of a MixPre :)
(http://www.sounddevices.com/images/products/mixpre_internal.jpg)
-
I'll throw my .02 in
Keep it simple and keep the cost down.
XLRs IN and Out (Maybe 1/8 or RCAs out)
6db stepped gain (most of us use recorders that can fine tune the levels)
Simple UV levels (3 or 4 meters - 24db,12db, 6db and 3db)
Power Switch
Trim Knobs, 10db pad and Clip Indicators would be nice too :)
If it sounds good and its reasonably priced, people will buy it.
i agree with this spot on. if space was an issue, i would understand the mini xlr's. but, i would prefer standard ones. meters are not that big of an issue, but sure are nice to stare at ;) stepped gain is fine also. i do like the idea of a power on light, and a peak light.
-
(http://farm4.static.flickr.com/3001/2578152568_7a7813d8b7.jpg)
Right now, the case I've chosen has ridges that prevents manual drilling of the mounting holes of a regular size XLR accurately. Using a mini-XLR will eliminate that problem.
But I do agree that is is more expensive. It's 3X more expensive!
I've thought of a solution of making a drill jig that will wrap the case and serve as a drill guide for the XLR holes, so the drill bit will not move or slide around. I'll test this solution, and if it works, then I'll be able to provide full-size XLR jacks on the sides... at just a minor bump in price for the additional manual labor involved.
I talked to the factory and unfortunately, they cannot do custom mods for the cases. So that means, I'll be the ones doing the case drilling.
Also, I just thought of an issue with these board designs (above and below)...
(http://farm4.static.flickr.com/3144/2578152546_299d6298eb.jpg)
I need some kind of support at the backend of the PCB to hold the weight of those 2 transformers.
-
wow just saw this thread
looks sweet
+T
i would agree thought that reg size xlr is a plus
i see the box you are using doesn't work right for them but if i was looking at buying something and i knew i had to get new cables or mod the ones i have that would play big time into if i got it or not
-
I decided to test my pre, powered by a 9V battery.
NOTE: I'm testing the pre without any optimization. Basically, I took the preamp designed for use with a 12VDC wall wart, and hooked it up straight to a 9V Battery.
This is the battery I used (bought at a grocery store). Duracell Coppertop 9V battery... costs about $10 for the pair, or $5 each.
(http://farm4.static.flickr.com/3179/2578701284_f1762e52ec.jpg)
CURRENTLY: The preamp is not optimized yet for battery use. Basically, the 48VDC-DC converter is running all the time even if phantom power isn't used. The PSU has an on-board LED mounted inside the case (that no one can see, it just serves as a reminder for me that there is input power)... the LED resistor value is low, so the LED consumes 5mA, the VU meter is running and operating... again with the LEDs using 5mA (low R value), the preamp is using DC servo instead of AC coupling. Again, these were things that didn't matter back then when I'm using a wall wart or a power transformer.
TO DO/FUTURE: To optimize the pre for future battery operation, I need to modify the phantom power switch so that it turns ON the 12V to 48V DC-DC converter only when phantom power is needed... instead of being ON all the time. I need to reduce LED consumption from 5mA to under 2mA... from my testing, the brightness is still good at less than half the consumption. I need to remove one of the opamp chips on the board and let the preamp run using AC coupling, instead of DC servo. That reduces chip count by one. (Or provide a switch so the user can toggle between DC Servo/AC Coupling.)
Again, typically... I expect to see a 12Volts input. But in this scenario, we'll just use an ordinary 9V battery.
(http://www.fivefishstudios.com/ffimages/BatteryPoweredPreamp.jpg)
We start at 9.1 Volts out of the box, hooked it up to the preamp with all the LED lights blazing, and VU Meters dancing. I used music material, and a movie material with lots of bass and explosions (Transformers :)) The VU meters got a real workout.
Total Running Time on a 9V Duracell battery: 225 minutes (or 3.75 hrs)
After that, the preamp shut down and stopped, i.e. no sound can be heard. Prior to that, even at 224 minutes, there is still full sound.
Power Consumption did not change whether the gain is at 6dB or higher. It's constant. However, the VU Meters with the bright LEDs, consume a lot of power (5mA per LED). Phantom Power is off on this quick and dirty testing. Single channel testing only.
As you can see from the graph, voltage was falling at a steady rate. And even when the 9V Duracell battery was only giving less than 7Volts, we still got 36 minutes operation out of the preamp (with all the VU meter LEDs running, etc).
ADDENDUM: When the pre shut down, I disconnected the 9V battery and let it rest for 15 minutes. Battery voltage climbed up from 6.5V to just a little over 7 Volts. Then I hooked it up again to the preamp and we got another 30 minutes life out of it.... then it shut down.
Rest the 9V battery for 10 minutes, and we got another 20 minutes operation out of it.
At this point I concluded my testing.
The current consumption ranges from 109 to 117mA. I'm a little surprised about this, since the preamp board is supposed to use only 17mA... and add 5mA for the PSU LED. I don't know how much the VU meter consumes though. It depends on the program material, and on how many of the 5 LEDs are lit up at any given time. Also, the (2) onboard DC-DC converter have a set minimum power consumption for it to operate. So add all those up, you get 109 to 117mA. Adding a second preamp channel shouldn't increase much power consumption, but adding a 2nd VU meter will.
I *think* I will ditch the VU Meter function and opt instead to use a signal and over/clipping indicator, using low-power opamps to do the job. Hmmmm.....
Also, just to put things in perspective... we're converting this ordinary Duracell 9 Volts input (down to 6.5 Volts) internally to a HIGHER split +/- voltages and even +48Volts.
You can't create a higher voltage from nothing, so the current consumption increases as the voltage falls down to maintain the same power equation... you know, Power = Volts x Current
In this case, total power consumption was less than 1 Watt the whole time! Ranging from 0.91Watts to 0.75 Watts.
In field use, most likely you'd probably be using a higher capacity battery (and not a 9V toy battery)... like a Li-Ion with 6800mAh, and not the puny 580mAh of a toy battery. I think it will be safe to say that you'll be able to tape concerts several hours long.
Until next time....
-
Nice work on testing. This is cool.
Richard
-
I *think* I will ditch the VU Meter function and opt instead to use a signal and over/clipping indicator, using low-power opamps to do the job. Hmmmm.....
I hope you leave it in, good metering IMO is a huge bonus. With the batteries we have available to us power isnt much of a problem when we are talking about the consumption of VU meters. Especially when you are getting almost 4 hours on a normal 9v w/ everything on. Whatever you do though, thanks for keeping us in the loop.
-
From my standpoint, it seems hard for a taper to calibrate an analog preamp (metering in dBu) to a digital recording device or A/D (metering in dBFS). So you can't really use meters on an analog preamp all that well for setting levels -- you need to use the meters on your A/D or recorder.
That said, to me it seems basic metering (albeit 2ch metering) is all that needed. I don't know the circuit ramifications or whether in the end it would save in current draw, but you could use bicolor LEDs. Something like this:
http://www.vishay.com/docs/83056/tluv5300.pdf
If you use 2 of these per channel, you'd only have 4 LEDs total, but could set them up so that you had for each channel one of these bicolor LEDs could show signal present at ~-24 (eg, Red) and stronger signal at ~-12 (change to Green), and the other LED could show near peak levels of ~-6db (Green) and approaching clipping of ~-2db (change to Red). [Sorry these db suggestions are my interpretation of dBFS, I'm not sure how this would play out with preamp. I guess you could start with the clipping point of your design and work backwards.]
-
Will this be available in kit form? Please?
If so, definately leave the option of metering in but switchable.
-
Todd, I'm thinking of using those kind of LEDs actually. But haven't thought of it for use in a VU. That's a novel way to use it. But it could be confusing if used as a VU as the user will see green/red, green/red.
What I'm thinking is show GREEN for signal present, and light up the RED for "pre-clip". Whatever is the exact level in between, I guess doesn't matter.
But the VUs do sure look pretty... makes me want to keep them.
bugg100
>>Will this be available in kit form? Please?
I don't know yet. We'll see.
-
Most of us agree that VU are not critical for a preamp. BUT, we all know that pretty lights do sell well.
"It is all about the lights!"
-
pretty lights do one thing thats a huge plus
they let you know fasssssst if there is a signal
they saved my ass once when i forgot to turn on phantom and i am looking down saying why am i showing a recording being made but i have no lights on showing there is an actual signal being recorded
i kept my svu1 for this reason (although now i don't really need it because the fr2le has lights on the side)
-
but what does it take to make an LCD display do what every one is asking for in lights and meters?
A LOT! :)
Well, you'll need a microprocessor (like a PIC or Atmel). A clock. Or pick a microprocessor with a built-in clock. Need a A/D converter, or a built-in one. Then the LCD display (usually a HD4480 compatible display). If the LCD does not use LED backlights, and uses the older style EL panel, then you need a high voltage DC converter too. And the chips will have to run either on 3.3 or 5V.
May be more trouble than it's worth if it's just going to be used as a VU. (Plus the clock circuitry, and digital data zipping by could induce RF which you'll hear as a whine in your amplified mic pre signal. )
Okay, I'll rethink the VU meters. I do like them... makes the unit "alive" instead of just sitting there.
-
i don't think meters should be a huge necessity. the lights also might not help in not so friendly situations. i personally like the look of the blue box with just xlr and knobs. but, i am just 1 of the 100's giving input.
-
I agree that metering is not a big need on a analog preamp. My Aerco has no lights. I've relied solely on the recorder's ADC and metering to get the job done. The results have been satisfactory as far as good clean unobstructed recordings go. Knowing your equipment is the key.
However, a single peak light would be nice.
+T fivefishdiy on your creation. ;D
-
Sure metering lights are great and all, but IMHO you dont need anything more than what the grace designs V2 had.
from the grace manual..
PEAK INDICATOR The LED peak indicator, which monitors the signal between the input
and output amplifiers, illuminates the green LED at -14dBu and illuminates the red LED at
+16dB (10dB before clipping).
plenty for a purely analog standalone portable microphone preamp..
-
PEAK INDICATOR The LED peak indicator, which monitors the signal between the input
and output amplifiers, illuminates the green LED at -14dBu and illuminates the red LED at
+16dB (10dB before clipping).
Eric.B! Hey thanks for that tidbit of info!
Guess what?! My existing VU meter's 5 LEDs denotes
–13dB, -7dB, 0dB, +10dB, +17dB
I can basically just use the 1st and 5th LED... and I basically have an instant -13dB and +17dB indicator... similar enough to the -14dB and +16dB indicators of the Grace.
If I'm going to do that, might as well put in the VU. (just thinking out loud)
-
Sure metering lights are great and all, but IMHO you dont need anything more than what the grace designs V2 had.
from the grace manual..
PEAK INDICATOR The LED peak indicator, which monitors the signal between the input
and output amplifiers, illuminates the green LED at -14dBu and illuminates the red LED at
+16dB (10dB before clipping).
plenty for a purely analog standalone portable microphone preamp..
I agree... Love the avatar BTW
-
Nice work ...
-
Parts arrived, Switchcraft mini-XLRs, locking DC jacks, mini-switches, knobs, spacers, stainless steel nuts and bolts to replace the cheapie screws that came from the factory... I think everything is starting to fit together.
Finished designing my VU meter last night, made it smaller. 1.25" tall x 1.6" wide.
(http://farm4.static.flickr.com/3277/2590440809_5fae4aee84_m.jpg)
Sending it out for prototype manufacturing.
This is how I plan to use the VU meters on the panel. (Artist rendition :))
(http://farm4.static.flickr.com/3284/2590501369_46975e3bce.jpg)
Check out the knobs... I sorta like it... kinda gives it a vintage look.
The buttons will probably end up being round, instead of square... we'll see.
Next step: Designing the main motherboard.
-
Looks tight! +T
-
Nice layout! Is that a switch to turn off the meters?
Very exciting to see this come together. I've been looking at your site previously (as well as Elliot Sound in Austraila) for pre-amp kits.
+T for listening to our feedback, pro or con!
Joe
-
Very nice. I've been watching from the sidelines all along but, I'm very interested in what comes of this.
Love the knobs.
-
the kind of lighting like the v2 the ad1000 is very simple to read and keeps u aware of whats going on. would love to see something of that nature. ed
-
bugg100
>>Is that a switch to turn off the meters?
Is that a *wanted* feature by most? I don't know yet... I know one of the switch will be for +48V phantom power. The other (2) switch functions are still up in the air.
Some options:
a) Polarity Reverse
b) VU meter on/off
c) Power on Switch
ero3030
Thanks for your input. Can you elaborate?
-
bugg100
>>Is that a switch to turn off the meters?
Is that a *wanted* feature by most? I don't know yet... I know one of the switch will be for +48V phantom power. The other (2) switch functions are still up in the air.
Some options:
a) Polarity Reverse
b) VU meter on/off
c) Power on Switch
ero3030
Thanks for your input. Can you elaborate?
Maybe
a) Phantom on off
b) High pass filter
c) -10 pad
-
Wow, looks great!
IMO, a pad isn't too useful, unless there is some worry that loud/strong inputs would overload the preamp on the input side.
Switches for power on, phantom power, and low cut (80Hz/6db) would be excellent.
If we can keep pushing you for refinements: it would be nice if you could structure the VU meters so that the bottom couple LEDs were green, then a couple yellow, and then only one red LED (well 2 since stereo) for approaching clipping. We will often be running our gear bags on the ground and looking down on them while standing, so it is helpful for the clip LED to really stand out from the other LEDs of the VU so that you can easily see it.
Thanks again for accepting all our input on this project!
-
i say minimize the front panel some. we don't need all the switches. i think 1 power switch and 1 phantom switch that works for both channels is all that is needed. i think the knobs look great, and could go either way with the need for lights.
-
a phantom switch on the front panel is asking for trouble I think. The ua-5 had that, and many a recording has been ruined by accidentally hitting that switch while trying to adj gain.
-
a phantom switch on the front panel is asking for trouble I think. The ua-5 had that, and many a recording has been ruined by accidentally hitting that switch while trying to adj gain.
IME with the grace v2 and grace v3, Ive never accidentally hit either one of the right or left phantom power switch..
-
I like switches, as opposed to buttons.
Phantom switch is KEY, some users might want to use it for other reasons besides taping.
HF Rolloff switch is a good idea to me.
An on/off switch too.
So that's 3 switches total. Little silver metal switches that are hard to switch to prevent accidental changes.
I feel it must have the LED metering, it looks cool but more importantly...it allows you to maximize the preamp signal going to the A/D and recorder.
I like Todd's idea of the 3 color metering. The proto-design looks really promising. Can't wait to see and hear the real thing.
-
Todd R
If we can keep pushing you for refinements: it would be nice if you could structure the VU meters so that the bottom couple LEDs were green, then a couple yellow, and then only one red LED (well 2 since stereo) for approaching clipping. We will often be running our gear bags on the ground and looking down on them while standing, so it is helpful for the clip LED to really stand out from the other LEDs of the VU so that you can easily see it.
That's reasonable. I'll check if they offer the green and yellow colors for this kind of LED. These are ultra high-efficiency Red LEDs, and does not need much current to light up like the normal LEDs.
Scooter and Nashphil
I'm debating on this very aspect too. I earlier did some "eyeballing" of clearances if I use a toggle switch, and it's a possibility.
The BIG difference is going to be added cost. 6 toggle switches is going to be more expensive than 6 mini-push button switches.
When it's time to design the daughter board, I'll be able to make the decision based on what fits inside the case.
My thinking is a "toggle" switch will be more at risk of being switch on/off rather than a push button switch when adjusting the knobs. Adjusting the knobs are left-right movement, (the same as toggling switches). Push button switches, you have to actually push in.... just my observation.
-
I should clarify that the bad ua-5 switch that i refer to is a pushbutton type switch. when i had a V2, i never had a prob with their toggle phantom switch.
"Adjusting the knobs are left-right movement, (the same as toggling switches). Push button switches, you have to actually push in.... just my observation."
true, but when you are "going in" for the level adjustment, you can easily depress one of those switches if it's in proximity to the gain knkobs ;)
-
Touché :)
Okay, no promises. I'll look into how this may affect pricing, and room availability inside the case.
-
I was thinking 3 toggle switches total. One for phantom, one for rolloff, and one for power.
The phantom and rolloff switches could affect both channels. Can't see a need to have individual switches for each channel.
For the left right thing, you could have the toggles go up down or left right. Really small, hard to swtich toggles is what I'm thinking.
-
I really like the layout of the Fostex FR2's power and phantom switches*, both on the right side with the XLR inputs. Since they are only used at the beginning and end of recording, they don't have to be readily accessible like rolloff, hp, meter switches etc. Perhaps put the power and phantom switches on the side with LEDs on the front (perhaps under one of the handles?) to indicate their state.
Appreciate your taking our input into consideration. Most of us have specific likes/dislikes that you won't be able to cstomize without actually building each unit custom. I hope you do offer a kit. That way those who purchase a kit can customize to their individual desires.
* http://www.fostexinternational.com/images/product_img/mid/fr2_right.jpg
-
Okay, before I get in too deep into this project, I want to test first if my PSU can handle 2 channels. I haven't tested the DC-DC PSU with 2 channels + 2 VU meters. So it was a little nerve-wracking to see if it will work or not.
;D Happy to say it works just fine. I have it powered for several hours now and it just barely gets warm. Touch with your finger the PSU chip and the little heat dissipates away, sucked away by your finger.
Did some load testing and measurements of current consumption.
Baseline: Power ON LED indicator ON. LED still using low-value Resistors, so LED current consumption is a little on the high side.
1 Channel Pre = 117mA @ 12VDC (1.4 Watts) <--- on our earlier 9V battery testing, we got the same numbers (117mA)
2 Channels Pre = 180mA @ 12VDC (2.1 Watts)
2 Channels + 48V Phantom Power ON for both channels (no mic load) = 200mA @ 12VDC (2.4 Watts)
2 Channels + 48V Phantom Power loaded with 2 condenser mics = 230mA @ 12VDC (2.7 Watts)
2 Channels + 48V Phantom Power loaded with 2 condenser mics + 2 VU Meters running = 240-250mA @ 12VDC (3 Watts)
(http://farm4.static.flickr.com/3268/2593480699_b2dc516bdb.jpg)
(http://farm4.static.flickr.com/3125/2594113640_c6fc9d2e59.jpg?v=0)
As I have no idea if this 250mA is good or bad, so I looked around the net for comparables. I found the V3 with a listed spec of 600mA with phantom power OFF, and AD converter OFF (and 1000mA PP ON, AD ON)
So I think the 250mA consumption running fully loaded is not bad at all.
Using an ordinary 9V toy battery, 580mAh, this gives us 2 hrs and 20 minutes running fully loaded.
Using a beefier 3000mAh Li-Ion battery, this gives us 12 hours. And with some DVD batteries, 6000mAh, this gives 24 hours of operation time.
Ok..I feel better now, and we shall continue.
-
Wow, that's virtually no power consumption. Since many of us use the 6000 dvd batteries to power our gear, that would mean we could run an entire festival on one battery.
Huge bonus.
-
Nice work!!!
Would you be willing to share your Phantom power generator circuit with us? I'm wondering what chip you use to get 48v?
Thanks for any insight...
Richard
-
Will this be available in kit form? Please?
If so, definately leave the option of metering in but switchable.
Another vote here, for a kit.
-
DUHHHH I am so Embarassed by this.... :-[ :-[ :-[
Let me explain.
A few days ago, I did the 9V battery test. Remember?
http://taperssection.com/index.php/topic,105112.msg1409154.html#msg1409154
I even remarked:
The current consumption ranges from 109 to 117mA. I'm a little surprised about this, since the preamp board is supposed to use only 17mA... and add 5mA for the PSU LED.
And then today I did the 2 channel test and measured current consumption. I got 250mA for 2 channels, full loaded, Phantom, VU, 2 mics connected, etc..
Guys... I am terribly sorry... the current consumption I wrote a few days ago and earlier today are ALL WRONG. (The 9V voltages from a few days ago are correct though.)
What happened?
So out of the blue, I decided to check if I'm getting 48Volts with 2 preamps connected and powered. I put the same tester I used for my current measurement, set it to voltage, move the jacks to the proper holes and I get a 63 Volts reading! So I kinda panic and tried to adjust it down the trimmer... then I decided to use another meter... I measure and now I'm getting 35Volts reading.... okay... what's going on? One of these meter is lying. But which one?
So I turned on my bench multitester and got 35V too. AHHHH!!!! That means, the first tester I've been using for current measurements these past few days is defective and giving me wrong readings...i.e. it's giving higher readings for voltage and current! :banging head:
I am so mad I chuck the thing in the trash! :flaming:
So now I repeat the measurements using a working meter.
Here are the NEW and CORRECT current consumption readings:
2 Channels, No Phantom Power = 130mA @ 12VDC = 1.56 Watts
2 Channels, with +48V phantom power, loaded with mics, plus VU Meters = 170mA - 190mA @ 12VDC = 2.2 Watts
So there you go... using a 9V toy battery, 580mAh, we'll get 3.0 hrs!
Using a 3000mAh battery, we'll get 15.75 hrs!
And using a 6000mAh DVD battery, we'll get 31.5 hrs!
So there you go....
As for me, I am going to treat myself and buy a real nice meter. Maybe a Fluke.
-
So what do you all think of this face plate for starters.........
Peace OOK
-
I like the centered text, maybe make a tad bit smaller.
Maybe a different and smaller font for "The Tapers Edition"... or even drop the "The" word
I don't like the quote symbols.
I really like the dB numbers in between the LEDs. That's good. I like that. (Arial font for clearer text.)
I don't know where I'm going to stick my logo. The brackets take up some of the room.
Thanks!
-
I like the centered text, maybe make a tad bit smaller.
Maybe a different and smaller font for "The Tapers Edition"... or even drop the "The" word
I don't like the quote symbols.
I really like the dB numbers in between the LEDs. That's good. I like that. (Arial font for clearer text.)
I don't know where I'm going to stick my logo. The brackets take up some of the room.
Thanks!
I think it's dead sexy.
I don't disagree with your critiques on the text, though.
-
where can i buy one and how soon can you deliver it to me?
rich
-
"As for me, I am going to treat myself and buy a real nice meter. Maybe a Fluke."
The work you are doing deserves FLuke. You will never be disappointed.
-
where can i buy one and how soon can you deliver it to me?
rich
Rich, It's not available yet... but will be available direct from my website. Thanks for looking.
-
The work you are doing deserves FLuke. You will never be disappointed.
I called in the order yesterday... so I should get my Fluke next week. ;D
I don't know about the *DESERVE* part, but I know I WANT it and after the wasted hours of work because of wrong readouts, I now know I NEED it . :)
-
Starting the design of the switchboard. Still need to add the 48V converter schematic on this board.
Screenshot:
(http://farm4.static.flickr.com/3250/2602518512_3728795bcf_o.jpg)
Here's my dilemna. So we'll have (6) switches...
(http://farm4.static.flickr.com/3284/2590501369_46975e3bce.jpg)
1st : ???
2nd: 48V CH1
3rd: Polarity Reverse CH1
4th: Polarity Reverse CH2
5th: 48V CH2
6th: POWER ON
I know you guys didn't ask for the polarity reverse, but I'm trying to see if I can design the switchboard for the homestudio users as well. Either way, if you *really* don't want it, I can just remove the switch and short the connection inside.
My *problem* is Switch #1. What could it be?
-
My *problem* is Switch #1. What could it be?
a few suggestions..
on/off switch for vu meter/lights
switch for m/s decoding... and have the switch work! ;D
have a peak hold reset button? then of course youd need a peak hold to begin with..
-
Starting the design of the switchboard. Still need to add the 48V converter schematic on this board.
1st : ???
2nd: 48V CH1
3rd: Polarity Reverse CH1
4th: Polarity Reverse CH2
5th: 48V CH2
6th: POWER ON
I know you guys didn't ask for the polarity reverse, but I'm trying to see if I can design the switchboard for the homestudio users as well. Either way, if you *really* don't want it, I can just remove the switch and short the connection inside.
My *problem* is Switch #1. What could it be?
I really don't see the need for two switches for 48V, one switch would suffice and be preferable to me. I think that the vast majority of us here would want a single switch for 48V.
I also think that the polarity reversal option is not one that would be desired by this group.
I would prefer toggle switches to pushbuttons too.
Thanks for asking for our input!! :)
1st : POWER ON
2nd: 48V CH1 & CH2
3rd: on/off switch for vu meter/lights
-
My *problem* is Switch #1. What could it be?
I am probably in the minority around here with this request...but if you have a spare switch, then I'd like to see a "ribbon" switch such as on the Grace m101 which is described at:
http://www.gracedesign.com/products/m101/m101.htm (http://www.gracedesign.com/products/m101/m101.htm)
or for those that would like to be safer in disabling 48v for extended periods of time without the chance of accidentally turning it on in the field...could there be an internal switch or jumper to disable the 48v circuitry?
-
I use ribbons alot too, and that would be really cool but maybe problematic to implement. I think the 48v on/off toggle is essential but I just see the need for one switch to operate both channels. Same with the HF toggle.
I don't ever flip the phase, even in the studio. If I need to do that I'll do it in post.
Truly poor mic technique if you need to flip the phase in the field, and you should retire from taping immediately.
-
Here's a summary of the above suggestions, features I think are important, what switch they go on is unimportant...
Essential -
1. Unit on/off :)
2. P48V on/off
Suggestions -
3. Metering on/off
4. Metering brighter/dimmer
5. High Pass (~80 Hz knee on/off)
6. Toggle P48V and P6V (for plugin power mics?) ... perhaps a disaster waiting to happen?
7. Stereo-linked limiter toggle on/off
8. Peak hold switch
9. M/S decoder switch
10. Ribbon mic mode (+48V phantom power is locked-out to prevent potential damage to ribbon microphones, the impedance of the mic input is raised from ???k Ohms to 20k Ohms)
11. 10 dB pad.
12. Test tone.
digifish
-
Starting the design of the switchboard. Still need to add the 48V converter schematic on this board.
1st : ???
2nd: 48V CH1
3rd: Polarity Reverse CH1
4th: Polarity Reverse CH2
5th: 48V CH2
6th: POWER ON
I know you guys didn't ask for the polarity reverse, but I'm trying to see if I can design the switchboard for the homestudio users as well. Either way, if you *really* don't want it, I can just remove the switch and short the connection inside.
My *problem* is Switch #1. What could it be?
I really don't see the need for two switches for 48V, one switch would suffice and be preferable to me. I think that the vast majority of us here would want a single switch for 48V.
I also think that the polarity reversal option is not one that would be desired by this group.
I would prefer toggle switches to pushbuttons too.
Thanks for asking for our input!! :)
1st : POWER ON
2nd: 48V CH1 & CH2
3rd: on/off switch for vu meter/lights
I like this method as well :)
But if you do go w/ 6 swicthes/toggles, I suggest the last one be a switch for the vu/metering to turn them on/off as well ;)
I LOVE the look of that box w/ those kickass switches :)
Does that one have transformers in it ??? I sure hope its at least an option!
-
Nice choice of omp!
I might just have to get me one; I haven't put a kit together since.... :hmmm: ..... an Eico 730 ?
(http://oak.cats.ohiou.edu/~postr/bapix/Eico730.jpg)
Is the portable stereo pre coming out as a kit, or are you assembling them?
-
Ok... thanks for the ideas and replies! Good stuff.
Okay, the extra switch will be used for VU Meter ON/OFF function. This actually makes sense as turning off the VU Meters will give you a bit longer battery life.
Also, all the switches have been replaced from the PushButton type, to the mini-Pushbutton type, to TOGGLE SWITCHES. ... per popular demand. I'm going to set them back farther also so you just have a small "stick" showing up in the hole. This makes accidentally toggling them a small chance.
ohr
or for those that would like to be safer in disabling 48v for extended periods of time without the chance of accidentally turning it on in the field...could there be an internal switch or jumper to disable the 48v circuitry?
Yes, there is an internal jumper. This should also save a bit of battery life if the 48V converter section is disabled.
Bean
Does that one have transformers in it Huh? I sure hope its at least an option!
Yep. It will be available with or without transformers. See this mockup photo.
The footprint will also allow the use of Cinemag or Jensen transformers. (of course, Jensen trafos will be more expensive)..... and *may* offer Lundahl transformer option too... (have to check if there is enough height and space clearance). The Lundahl option will probably be more expensive than the Jensen as it will involve additional hardware parts.
(http://farm4.static.flickr.com/3001/2578152568_7a7813d8b7.jpg)
-
Nice choice of omp!
I might just have to get me one; I haven't put a kit together since.... :hmmm: ..... an Eico 730 ?
Man, you must be old. I put an Eico together, mono, in HS. And it worked! 8)
-
Ok... thanks for the ideas and replies! Good stuff.
Okay, the extra switch will be used for VU Meter ON/OFF function. This actually makes sense as turning off the VU Meters will give you a bit longer battery life.
Also, all the switches have been replaced from the PushButton type, to the mini-Pushbutton type, to TOGGLE SWITCHES. ... per popular demand. I'm going to set them back farther also so you just have a small "stick" showing up in the hole. This makes accidentally toggling them a small chance.
ohr
or for those that would like to be safer in disabling 48v for extended periods of time without the chance of accidentally turning it on in the field...could there be an internal switch or jumper to disable the 48v circuitry?
Yes, there is an internal jumper. This should also save a bit of battery life if the 48V converter section is disabled.
Bean
Does that one have transformers in it Huh? I sure hope its at least an option!
Yep. It will be available with or without transformers. See this mockup photo.
The footprint will also allow the use of Cinemag or Jensen transformers. (of course, Jensen trafos will be more expensive)..... and *may* offer Lundahl transformer option too... (have to check if there is enough height and space clearance). The Lundahl option will probably be more expensive than the Jensen as it will involve additional hardware parts.
(http://farm4.static.flickr.com/3001/2578152568_7a7813d8b7.jpg)
Ok... thanks for the ideas and replies! Good stuff.
Okay, the extra switch will be used for VU Meter ON/OFF function. This actually makes sense as turning off the VU Meters will give you a bit longer battery life.
Also, all the switches have been replaced from the PushButton type, to the mini-Pushbutton type, to TOGGLE SWITCHES. ... per popular demand. I'm going to set them back farther also so you just have a small "stick" showing up in the hole. This makes accidentally toggling them a small chance.
ohr
or for those that would like to be safer in disabling 48v for extended periods of time without the chance of accidentally turning it on in the field...could there be an internal switch or jumper to disable the 48v circuitry?
Yes, there is an internal jumper. This should also save a bit of battery life if the 48V converter section is disabled.
Bean
Does that one have transformers in it Huh? I sure hope its at least an option!
Yep. It will be available with or without transformers. See this mockup photo.
The footprint will also allow the use of Cinemag or Jensen transformers. (of course, Jensen trafos will be more expensive)..... and *may* offer Lundahl transformer option too... (have to check if there is enough height and space clearance). The Lundahl option will probably be more expensive than the Jensen as it will involve additional hardware parts.
(http://farm4.static.flickr.com/3001/2578152568_7a7813d8b7.jpg)
what r u going to do for your 2nd trick!!! ;D this guy has something goin on!!
-
Just read through the whole thread and look forward to watching the continuing development. Looks great. Fantastic feedback/design process. ;D
I don't have much to add other than the suggestion that if the layout allows, it would be great to have all the connections on one side, which I think would greatly aid in cable routing in the bag. The inclusion of an unbalanced 1/8" stereo output in addition to the XLR's would be both convenient for running into small mini-jack input flash recorders (either as the primary recorder or as a backup) and also allow for easy patching out to others if using the XLR outs.
Thanks for the good work!
-
PM sent on a stereo pre with Lundahls, kit or assembled...
between the That Op-Amp and the Lundahls, I need to hear this thing, no question
Boojum-
The Eico 730 is an A.M. Modulator, as in A.M. radio broadcast, for, in this case, ancient Ham radios.
It was way before my Hi-Fi listening days.
We did modify the amp for high fidelity instead of high intelligibility. This caused much consternation by other Hams as it was bandwidth intensive in their eyes. This was not completely the case, as A.M., in general is a bandwidth hog, but not nearly as bad as F.M.
But I digress! I want to hear the Lundahls in a portable Pre!!!
-
I agree with gutbucket here. All connectors on the same side or preferably the back.
I like the stereo-mini output idea. (1/8 plug)
I thought I saw mention of mini-XLR's. I would not go that route unless absolutely critical. I would think that would actually discourage sales and I certainly wouldn't want to have a set of expensive
Right Angle mini XLR's made up. I would actually use another frame if that were the case. I love the blue case, but if you can't make it work easily, don't force it and certainly don't add work to your end by having those difficult to drill holes. There are other cases that might work, or you could make the design and have the case prefabbed like Grace does with his.
I'm loving the design and feedback process. I look forward every day to seeing the next step.
BTW yall, FiveFish has graciously offered to let me try out one of this 4 ch transformerless designs in a few weeks.
I plan on using it for a record I'm starting July 22, so I'll be sure to post some reports and sound clips.
-
BTW yall, FiveFish has graciously offered to let me try out one of this 4 ch transformerless designs in a few weeks.
I plan on using it for a record I'm starting July 22, so I'll be sure to post some reports and sound clips.
Looking forward to that. More of what really counts most.. the sound.
-
wow! just saw this, looks great. I wanted to put in a third vote for all connectors on the back
if power consumption is a big deal, you might want to consider having a 12V phantom circuit via internal jumpers as well. schoeps and i believe several other mics run fine on 12V phantom
-
+T This is great watching some one design a pre-amp in almost real time. Almost like watching American Chopper :)
Nice design
Comments:
1. I would suggest All connectors on same side preferably back
2. I would make two version one with transformers and one without (or as you have said make input/output transformers an upgrade option with add on board)
3. Unbalanced out would be a nice addition on a gold plated 1/8" jack - lots of people run Edirol R-09's which take unbalanced in's
4. Selling as a kit would be nice as well for those who like tinkering
5. External Power supply - as others have said 9V preferably - 12V is not too bad using Lion batteries but alot more 7.2 - 9V avail these days with DVD players and RC Car popularity
6. Metal poly film Caps as an option instead of electrolytic caps with audio signal circuit
If these have already been discussed, my apologies
-
Finished the PCB for the switchboard/48V supply. I can already see 3 changes I need to make. Mechanical dimensions and exact placement of switches, holes not yet finalized.
I just need a few more days to mull this over, review it, criticize it, edit, change until I'm satisfied, then off to prototyping. It costs a few hundred dollars per prototype run. And no matter how much I reviewed each revision, it takes me about 3-4 prototypes to get it to where it's really finished and ready for production.
The preamp also has soft-start 48V, meaning the 48V is raised gradually to avoid the THUMP when turning on or off phantom power. It also protects your expensive mic from a sudden 48V surge. And if you accidentally turned PP on, you can turn it off immediately and your mic wouldn't get the full 48V across it.
O-Canis
Those switches are kinda expensive. So trying not to go there. My switch will have a solid feel to it. Not wimpy. LED lights are separate from the switch.
Gutbucket and nashphil
I actually prefer all XLRs on one side too, i.e. the back. I probably misunderstand this thread. I thought the consensus and preferred way was XLRs on the sides?
Either way, I think it will be possible to offer it with XLRs on the sides, or the back. XLRs on the sides will just cost a little bit more (because of the additional manual labor).
I like the stereo-mini output idea.
This may be doable. The rear panel okay? If I can find space on the front panel, it will go on the front panel.
Re: Mini-XLRs
Again, can be offered as an option. Since the XLR jacks will be connected to the PCB via flying leads, we can have any jack format you want. TRS if you want, or mini-XLR or full-size XLR.
nashphil
offered to let me try out one of this 4 ch transformerless designs in a few weeks.
Sorry, I still don't know where my 2 (4)-channel rack units are. They're floating somewhere in Nashville. So you'll probably get the 1-ch pre to play with.
campbrs
1. See answer above.
2. The options are: No transformers, with Cinemag, with Jensen, with Lundahl (maybe).. Also with XLRs on the side or back, or mini-XLR if you want. Each option will be priced differently.
3. The balanced output of the pre can be used with unbalanced inputs. Just use pin 2 and 3. My balanced driver "behaves" like a transformer, even though it's solid state.
4. Kit? We'll see how easy or hard it is to build. Otherwise, I may spend a whole lot of time handholding kit builders.
5. The pre will still operate down to 6.5Volts during my testing. But ideally, 12V is preferred though 9V will also work (down to 6.5V). See a previous post of mine... 9V Battery Duracell testing a few pages back.
-
4. Kit? We'll see how easy or hard it is to build. Otherwise, I may spend a whole lot of time handholding kit builders.
One thing about introducing this as a kit to this community, you'd see a lot of self-sufficiency amongst the group. A couple threads would pop up for people to discuss questions, problems, etc. and those with greater skills would probably be quite a bit of help to those who may
find themselves in over their heads.
-
4. Kit? We'll see how easy or hard it is to build. Otherwise, I may spend a whole lot of time handholding kit builders.
One thing about introducing this as a kit to this community, you'd see a lot of self-sufficiency amongst the group. A couple threads would pop up for people to discuss questions, problems, etc. and those with greater skills would probably be quite a bit of help to those who may
find themselves in over their heads.
No shortage of hand holders in this group...and I mean that the nice way!
-
once again, this looks great. i don't think you need so many options. stick with regular xlr's. pick a side for them and stick with it. only offer 1 type of transformer. the more options you give the people here, the more work for yourself. there are a lot of opinions here, and all differ slightly. i would hate to see you run into the ground trying to customize these boxes. also, i would think you will need different names for the transformer one. maybe TST-2 w/ transformer, and TS-2 without,
-
i for one wouldn't buy a kit because i don't have the knowledge to put it together right
i also would be worried about buying a used kit based on not knowing if the person who put it together knew what they were doing
but its a great idea for those who want to play around, for my money though get it from the maker direct
-
Gutbucket and nashphil
I actually prefer all XLRs on one side too, i.e. the back. I probably misunderstand this thread. I thought the consensus and preferred way was XLRs on the sides?
Either way, I think it will be possible to offer it with XLRs on the sides, or the back. XLRs on the sides will just cost a little bit more (because of the additional manual labor).
I like the stereo-mini output idea.
This may be doable. The rear panel okay? If I can find space on the front panel, it will go on the front panel.
You'll likely not want to offer too many options and the choice of which is your own business decision to make. The option for side connections is a big part of the attraction in my mind and would diferentiate this product form others I think, though I completely understand that rear connections would better accommodate rack mounting home or studio users and perhaps others here too.
For field recorder preamp use, most of us keep the equipment in a bag of some sort, with the face pointing up. Because of that, cables out one side of the unit makes the connections more accessible and keeps the weight of the unit off of those connections. Most here devise ways of reducing the stress on connectors that do exit the bottom of the equipment- by using right angle connectors, attaching the gear to DIY internal racks or by attaching ears or handles to the back to bear the weight of the device and to allow the connected cables to bend without weight on them. Devising that sort of protection and support isn't as critical if there is nothing on the back of the housing. To me, the aspect of all connections on one side instead of the back really denotes this piece of gear as well designed for this type of field use (along with being DC powered of course).
Obviously for typical rack mounting, connections at the rear are preferable. Some here may prefer that configuration because they have already made provisions for taking care of cabling out the bottom of the gear in their bag. After all, most professional audio equipment is designed or descended from a rack mount mindset.
The stereo mini output would be fine either on the front face if there is room, or on the same side as the other connectors. I will say that if any connections are going to end up at the back of the unit I'd suggest something like the handles on the front, feet or some sort of recessed panel/ extended case sides that are deep enough to support the weight of the box and keep it level, and that are deep enough to provide clearance for standard right angle connections (XLR, mini-jack, power, whatever). One problem many of us have with the Grace V3 is its connectors located on the back - using right angle XLR's for the audio signals is not too much of a problem, but a right angle version of the locking power connector is not available. That places a lot of stress on the power cable sticking out farther than anything else on the back unless the unit is supported somehow. Again, most DIY a solution or build a custom cable with serious strain relief. Still, you usually have to pull the unit completely out of the bag to access any of those connections. I use short right angle input extension cables so that I can leave everything connected back there and live with the extra XLR cable connection points in the mic cables so I don't have to pull the preamp out to connect mics, then re-wedge foam in the bag that surrounds and supports everything.
-
Again, thanks for the feedback.
Offering the stock, Cinemag and Jensen trafos won't be too difficult (except for the capital required, i.e. me buying 2 types instead of just one type). So most probably, the initial offer will be STOCK, and CINEMAG.
The Lundahl option will come later. Depending on demand, if any...
Offering the side XLR option is something that may also come later. So initial offer will be XLRs in the rear.... because that is something I can easily program on my CNC and make easily.
What I'm just saying is the XLRs are not PCB mounted so changing placement is not a big problem. (* a second revision of the PCB down the road and I may use PCB mounted XLRs if the demand for rear XLRs outweigh the side XLRs... but that's speculating that this pre will even be wanted.)
Gutbucket
I think it will be easy to rig and bolt 2 legs to the backside of the case. Just need an L-shaped aluminum or steel material, drill 2 holes on the L-plate, and screw to the backside using the existing screws on the case.
Will try that sometime... thanks for comments.
-
:cheers: and :headphones:, i'm luvin this process ;D ed
-
Update for today: Got some time to work on the board, now 99% done, just need to verify a few measurements.
(http://farm4.static.flickr.com/3164/2608451055_17ff6990e9_o.jpg)
-
^^ What chip are you using for Phantom on that board?
Richard
-
illconditioned
it would be nice if this project stays open.
If you buy any of my kits, the SC-1 preamp (which this new TS-2 preamp is based, but with just a different footprint), or my Power supplies, VU meters, Active DI and others, you get the bill or materials, schematics and instructions on how to build them. You also get the PCB, and all the parts.... including the screws and nuts and fuses. So I don't know how much more "open" I have to go. The only thing I don't provide is the soldering iron and lead.
I'm doing a blow-by-blow update on the development of this pre... I don't know how much more open I need to do.
Now, my current DC-DC converter is not released either as a kit or a running product out there in the "wild" yet. I'm not ready to release it yet. In fact, just a few days ago, I've thought of a different way of generating 48Volts and in the process of verifying the new method. So the 48V section you see here may probably still change. Depending if the new method will be better than this or not. This is my 5th revision of this converter PSU. It was already working fine in the 3rd revision... but was not happy with the amount of noise it was giving out... not when you put this beside a high gain pre inside a small case. So it took 6 revisions to get to where I'm "satisfied" with it. (Had to throw out 100 good PCBs of the 5th revision, costing hundred$ of dollar$, since it didn't pass my muster!) .... now, I'm thinking of doing a 7th revision. So nothing is final yet until the fat lady sings. :)
Hope you understand.
mshilarious
<thumbs up!> :D
-
^^ OK, someone said (in a PM) that I should not criticize fivefish, for lack of schematics, or detailed technical information.
I am not criticizing, just expressing *my* opinion that sharing information is good. I still admire fivefish's work and encourage him to continue with his fun blog as well.
Richard
-
I on the other hand have worried that he was sharing too much "inside baseball" info that might be of value to competing product developers. But, knowing that it will all likely be available in kit form eventually sort of brings the wizard out from behind the curtain. As far as I'm concerned, what he's showing me is beyond my comprehension and what I think he really wants is some virtual field testing done before too many PCBs get burned and ultimately tossed out. If we can give him a good sense of what qualities a good/great field pre should have, then that's invaluable input from my perspective. Any trial and error work that can be eliminated will ultimately (hopefully) keep his price down to a reasonable level so that we can all buy the thing.
As far as I can tell, it is all about finding the market. Look at what Chris Church has done! He's offering exactly the product we want, at a great price, and... he's hanging around to support it. What more can you ask for.
Admittedly this preamp will probably sell less units, but I think the same philosophy will work.
As far as disclosing information, any real competitor can easily buy and/or dissassemble the product. This is not rocket science. 90% or more is just getting what people want.
Anyway, I wish both fivefish and Chris Church the best of luck. If only more companies took their customer input so seriously...
Richard
-
I've been following this thread from the beginning and I must say that fivefish lost me a long time ago with the technical stuff. Many others may be able to reproduce what he is doing from what he has written here, but they aren't doing it here. If someone came up with a copy of this pre and tried to sell it here for less, I would still lean towards this one as he came to us for input. He didn't try to steal someone else's work and then market it to us.
+T Fivefish
-
...So nothing is final yet until the fat lady sings. :)
Did the fat lady really sing if no one pulled tape of it? ;D
I'm really glad to hear that you are willing to put time into getting this thing right.
The effort invested upfront may ultimately payoff.
The new technology has made it possible to put out a Pre that's a cut above, for less than ever, and I'd love to see it happen.
Good luck... and I am serious about the Lundahl option.
I think that presence is under-appreciated, and would venture a wild guess that Lundahl-Schoeps might just be a killer combination.
BTW, does anyone know what Len (Core) based the 2Phant circuit on?
How about the Deneke PS-2 circuit?
They both seem to do "quiet" very well.
-
Okay... been busy this afternoon... :)
... trying to rack a 1-channel SC-1 Solo version.... so if you want to imagine the 2-channel TS-2 version, well just double what you see here.
Designed the front and rear panels, setup hole dimensions and locations... then created the CNC Gcodes.
(http://farm4.static.flickr.com/3114/2616619453_9d09938d59.jpg)
This is the front panel layout. You can see the holes for the brackets, gain, trim, switch and LED.
(http://farm4.static.flickr.com/3060/2616619497_0330c67f31.jpg)
Before I can even mill the aluminum panel, I need to create a jig out of MDF. Then I drop the panel inside the pocket I created and screw it to the board.
If you want to see how my panels are milled, see this related video: http://www.youtube.com/watch?v=uA0xwIE4xdI
And this is the finished CNC-milled panel.
(http://farm4.static.flickr.com/3290/2617441872_5fb937b783.jpg?v=0)
Just look at that XLR hole... it's perfect! :)
(http://farm4.static.flickr.com/3196/2617441894_917f71c003.jpg?v=0)
I told you the fit is perfecto-mundo! :)
[skip the boring stuff, screwing holes, etc...]
(http://farm4.static.flickr.com/3030/2617441996_708c809cf9.jpg?v=0)
And here's the finished 1-channel preamp... powered by a Tekkeon battery.
(http://farm4.static.flickr.com/3083/2616619703_2db156ff57.jpg?v=0)
Closeup shots of the back.
(http://farm4.static.flickr.com/3182/2616619841_e873fdcce0.jpg?v=0)
And here's another beauty shot...
That's all folks.
Next.... I'll try to finish the (2) channel prototype... but I need to wait first on the VU meter boards from the factory. I need to verify clearances on the switchboard PCB. If everything's good, we send out the switchboard PCB for manufacturing while we start design on the main motherboard.
-
Awesome stuff. Love the progress, keep up the good work. We really do appreciate it.
-
my only other suggestion is some sort of locking switchraft power connector (ala v3), or a retainer clip for the power cable (ala minime)
Awesome stuff. Love the progress, keep up the good work. We really do appreciate it.
-
my only other suggestion is some sort of locking switchraft power connector (ala v3), or a retainer clip for the power cable (ala minime)
Awesome stuff. Love the progress, keep up the good work. We really do appreciate it.
Hey jerry, I do have the locking switchcraft jack. I just didn't use it for this prototype. (I don't have a corresponding power source to use with that jack.)
-
my only other suggestion is some sort of locking switchraft power connector (ala v3), or a retainer clip for the power cable (ala minime)
Awesome stuff. Love the progress, keep up the good work. We really do appreciate it.
Hey jerry, I do have the locking switchcraft jack. I just didn't use it for this prototype. (I don't have a corresponding power source to use with that jack.)
FWIW, I've had great luck just using a hot melt glue gun and some gaffer's tape and putting at the point where the (right angle) power connector meets the wire. I've done this on any rig I've used, Edirol UA5, R4, R09, and lots of other stuff. More or less permanently attaches the plug. Not elegant, but works with any gear.
By the way, will those locking connectors work with standard power supply connectors? Are they like the ones on the Dmic20? If so, putting a locking jack on the gear would satisfy all of us.
Richard
-
Not sure what the Dmic20 looks like.... but the ones I got are the Switchcraft DC jacks 2.5mm with nut.
Yes, they work with plain-vanilla, normal DC jacks.
(http://farm4.static.flickr.com/3057/2618753207_5502dda5a0.jpg)
These are panel mount so it's easy to add it anytime, or even do it as a mod by the user.
-
That's the stuff.
The Sound Devices MP-2 has that same jack/plug combo.
-
my only other suggestion is some sort of locking switchraft power connector (ala v3), or a retainer clip for the power cable (ala minime)
Awesome stuff. Love the progress, keep up the good work. We really do appreciate it.
Hey jerry, I do have the locking switchcraft jack. I just didn't use it for this prototype. (I don't have a corresponding power source to use with that jack.)
How about a four-pin XLR for power?
Cheap, bomber, and easy to get:
(http://www.designnotes.com/Merchant2/graphics/00000001/CA108.JPG)
(http://www.performanceaudio.com/images/products/143/2636.jpg)
-
I think that 4-pin XLR jack will be overkill. Since we only need 12V and a ground. The locking Switchcraft DC jack does the job.
Now, if you're building a remote PSU that needs to supply +18, -18, +48 and GND... that 4-pin XLR jack is perfect.
-
Not sure what the Dmic20 looks like.... but the ones I got are the Switchcraft DC jacks 2.5mm with nut.
Yes, they work with plain-vanilla, normal DC jacks.
(http://farm4.static.flickr.com/3057/2618753207_5502dda5a0.jpg)
These are panel mount so it's easy to add it anytime, or even do it as a mod by the user.
That Switchcraft DC jack is a good screw-on, locking connection, but the problem for our applications is that it is not available as a right angle connection. That's the one used on the V3 which ends up sticking out the back farther than anything else and can end up crushing the power cable entry to the connector. Again, not as big a problem if used on the side of the unit, but even on the side, many would prefer a connector that has a right angle option. That's the only real advantage of the 4-pin xlr that I can see.
-
might i suggest the poss of putting some of those black "U" on the back too
it would give people something to rest on instead of the cables when running upright
looks good
-
I love this thread!
Thank you all.
-
Actually right angle Switchcraft locking type connectors are available from Remote audio and nonlocking right angle are available from Mouser.
David
-
might i suggest the poss of putting some of those black "U" on the back too
it would give people something to rest on instead of the cables when running upright
looks good
I tried the above suggestion. Photo here:
(http://farm4.static.flickr.com/3273/2622379669_584329b90e.jpg)
You can also see the locking Switchcraft DC jack that I installed.
Re: the brackets at the back. I find that they interfere with right-angle XLR jacks. Not unless you turn the jacks so the cable come out of the top or bottom, instead of the side.
Plus, beside... if you use a right-angle XLR jack, the depth of the XLR jack already provides protection to the DC jack.
Now, if you use a straight XLR jack, the jack is longer than the brackets anyway so the brackets at the back are really of no practical use.
So I'm not sure if I'm going to go for that on the final product. Good suggestion though, and I did gave it a try... but I'm not fully convinced it's useful.
Added LED panel mount indicator for the front panel and replaced all bracket screws with Stainless steel ones. The PCB is also attached to the case with spacers and screwed to the bottom with recessed stainless head screws. This PCB ain't going anywhere... considering the fact it's also bolted to the front panel via the Gain and Trim pots screws.
It's solidly built.
(http://farm4.static.flickr.com/3252/2622542541_50b19ef851.jpg)
Tekkeon Battery:
On a different matter, I've been playing with this Tekkeon Battery with the adjustable outputs and I find that they give a fairly good amount of RF interference.... I noticed this when I laid the battery on top of the input mic cables, with volume set at max and gain at max 72db. I can hear RF noise. It's not noticeable though at lower gains, 60dB and below.
The RF noise is not there if I use a DC wall wart adapter or plain 9V battery. It's definitely coming from the Tekkeon battery pack.
-
I noticed this when I laid the battery on top of the input mic cables, with volume set at max and gain at max 72db. I can hear RF noise. It's not noticeable though at lower gains, 60dB and below.
Can you describe the noise? A ticking or something with a regular period of repetition?
-
The RF noise is not there if I use a DC wall wart adapter or plain 9V battery. It's definitely coming from the Tekkeon battery pack.
Just a note OZPeter saw the same thing in R44 testing, when he laid a video-battery-pack next to his mic.
http://taperssection.com/index.php/topic,103270.msg1406905.html#msg1406905
BTW Off Topic: While all the EE savy people are in this thread, I found something odd with the R09HR mic in, if anyone has any ideas I'd love to hear them (not in this thread obviously :) ).
http://taperssection.com/index.php/topic,105893.msg1418503.html#msg1418503
digifish.
-
Can you describe the noise? A ticking or something with a regular period of repetition?
Neither. It's more like a very high pitched whistling sound... like a faint whistling of a water kettle.
It's definitely coming from the Tekkeon. I unplug the Tekkeon, without changing the gain setting, wiring, or anything... plug in a wallwart (which is also a switching PSU design) and the wall wart didn't exhibit this said noise.
... now just to give you guys an idea, I'm splitting hair here when I said I heard the noise. At 72dB gain setting, we're talking 4,000x amplification of the signal. If you connect a microphone at the end of that cable and the mic is picking up sound around, this noise will get buried way way under by the audio signal.
-
Inaudible when there's signal present or not, it's still something to be avoided. You say it happened when the battery was atop the pre? did you pick it up when they were separated?
/me thinks about lead-lined padding in his bag.
-
You say it happened when the battery was atop the pre?
No, when the battery was atop the input mic cables.
The preamp's case (aluminum) is completely grounded and doesn't make the noise louder or softer. The aluminum case is shielding the pre from external RF noise.
But if the noise is injected into the mic cable coming in, then it becomes part of the signal. Amplify that little noise 4000x, and you'll hear the faint sound. There is some CMRR going on, so the noise is reduced by the balanced input lines but my guess is the battery is not completely shielded. I'm going to try a different mic cable too.
I'd probably also try other battery brand/models (i.e. a simpler battery without push button voltage selector) to see how those behave.
-
You say it happened when the battery was atop the pre?
No, when the battery was atop the input mic cables.
...
I'd probably also try other battery brand/models (i.e. a simpler battery without push button voltage selector) to see how those behave.
Perhaps it's time for the fivefishdiy high-fidelity 'battery back' to go with the preamp
Something that takes 8 AA's should provide enough juice ;D
digifish
-
Don't know if you saw my earlier posts about battery testing.
2 Channels, with +48V phantom power, loaded with mics, plus VU Meters = 170mA - 190mA
... using a 9V toy battery, rated 580mAh, we'll get 3.0 hrs!
Okay, parallel (2) 9-Volt Duracell batteries for a 6 hr usage life. :D
-
I think that 4-pin XLR jack will be overkill. Since we only need 12V and a ground. The locking Switchcraft DC jack does the job.
Now, if you're building a remote PSU that needs to supply +18, -18, +48 and GND... that 4-pin XLR jack is perfect.
I can't imagine where I'd find that.
But back to the Pre-amp.
I'd prefer to have over-kill in durability for a measly extra $4 in parts
It wouldn't be the first Pre to run 12vdc through an 4-pin XLR if you did it.
It also allows for a combo 12/6vdc supply for, say, an external ADC or recorder.
I always upsize my power source because I get more useful life as the rechargeable cells will drop to 80% of capacity in a relatively short amount of time.
From the Archive...
4 Pin XLR Pin assignments:
6V:
3 is hot (+ 6v)
Pin 2 is ground (-)
12V:
Pin 4 is hot (+12v)
Pin 1 is ground (-)
Designing for disposable batteries isn't the most environmentally friendly option.
If you used rechargeable 9volt cells instead, do you think it will go a full six-hours?
-
The nice thing about my design is the flexibility in customization.
It can be a custom mod offered as an option. Where the locking Switchcraft DC jack shown here, can be replaced with the 4-pin XLR.
(http://farm4.static.flickr.com/3273/2622379669_584329b90e.jpg)
But just to be clear, it's not going to be just a $4 addition in the price. The math doesn't work that way. Now there's (3) new holes to be drilled, and manual labor (and time) for soldering wires from the PCB to the XLR pins... which is very slow (vs. soldering the PCB mounted DC jack), screwing it on, and keeping also a new part in stock on the shelves.
4 Pin XLR Pin assignments:
6V:
3 is hot (+ 6v)
Pin 2 is ground (-)
12V:
Pin 4 is hot (+12v)
Pin 1 is ground (-)
Whose standard is this??? ^^^ Just curious.
I don't have a need for a 6V supply, so pin 2 and 3 will probably be unused.
UPDATE: Is the Panel mount XLR jack a MALE? or a FEMALE?
Looking at the jack (rear view), which pin are you calling Pin #1? (leftmost, or rightmost)? and about pins 2,3,4... Clockwise? counterclockwise?
-
The nice thing about my design is the flexibility in customization.
Very true, and being a kit, it really lends itself to "tweaking" to one's liking
4 Pin XLR Pin assignments:
6V:
3 is hot (+ 6v)
Pin 2 is ground (-)
12V:
Pin 4 is hot (+12v)
Pin 1 is ground (-)
Whose standard is this??? ^^^ Just curious.
I don't have a need for a 6V supply, so pin 2 and 3 will probably be unused.
Yes, but it can be used for a 6vdc device, like an MTII or some other recorder.
One PS, feeding multiple components
As to who made that a standard, I am unsure.
It was posted by one of the Moderators on the board, so I'm pretty sure that it is valid.
The caveat is that the Eco-Charge four pin is wired differently, uses a jumper between two pins.
Perhaps a "de facto" standard, by a bunch of tapers who needed 6/12vdc?
Maybe someone can jump in here? Any reason the 4 Pin XLR was listed as a 12V standard?
-
Actually right angle Switchcraft locking type connectors are available from Remote audio...
Really?
Cool, that's news to me.
Couldn't find them on their site. Suppose I could drop them a line and ask though.
-
BATTERY TESTING PART 2:
I hooked up the preamp to the Tekkeon battery starting about 2pm this afternoon and left it ON all day, playing music.
It's now 10:30pm and the Battery is still going strong, and the pre still working.
(There are 7 LED indicator lights on the battery, hooked it up at 2pm with only the 6th indicator lit (i.e. 70-85% charged). Now, at 10:30pm, the 6th LED indicator is off, and the 5th indicator is lit (indicating 60-70% remaining charge).
So far, that's more than 8 hours of operation time... And I think there's a good several more hours of battery life left here.
I'm satisfied. ;D
-
UPDATE:
The Fedex guy visited me this morning with some goodies. It's the VU-Meter PCBs. Size is about 1" x 1.5". Could be made smaller but I need 1/8" holes for mouting.
VU has on-board voltage regulator, wide supply voltage range (up to 6 to 24VDC) and on-board trimmer for 0dB adjustment.
Built one prototype quickly to see if my design works, and yes! Success!
(http://farm4.static.flickr.com/3016/2629282742_2442a08f0e.jpg)
And a photo with the VU meter in action. (Sorry for the lousy photo... hard to photograph it clearly and still have the LED lights visible.)
(http://farm4.static.flickr.com/3032/2628464625_5918aa4997.jpg)
-
I'm maybe misinterpreting the range on the second "live" VU photo, but should I be interpreting the +17 db value as = 0db/clipping?
I look forward to these updates every day! ;D
if it were a vu meter giving you the level of the input to a digital recorder.. then yeppers!
-
I'm maybe misinterpreting the range on the second "live" VU photo, but should I be interpreting the +17 db value as = 0db/clipping?
I look forward to these updates every day! ;D
if it were a vu meter giving you the level of the input to a digital recorder.. then yeppers!
it's really going to depend on the sensitivity on your recorder or A/D converter. For example, when the 722 is set to line-in and 0dB, it hits 0dBfs (digital clipping) at +20 dBu. So if you hit +17 dBu on the pre-amp, you know that you'd never hit digital clipping. (in that situation, you'd want to use some gain on the 722, so that you hit digital clipping before you overload the pre-amp). Of course, other recorders vary on their input sensitivity, and in fact, most would probably digitally clpi well before +17dBu, in which case you know to just watch the meters on the deck or A/D converter, and as long as you weren't digitally clipping, you would know that you are not overloading the pre-amp, and you could basically ignore the LED's on the pre-amp.
-
I'm maybe misinterpreting the range on the second "live" VU photo, but should I be interpreting the +17 db value as = 0db/clipping?
No... +17dB is NOT clipping on the preamp. (Just because it's a RED led doesn't mean it's clipping.)
The max headroom of my balanced line output driver chip is +27dBu. But since I'm running at a reduced voltage supply (instead of +/- 20VDC), I would estimate my max output headroom to be +22dBu (approx. 27.6 Volts peak to peak).
So that +17dB on the VU meter is still a good 5dB away from clipping.
EDIT: So I guess using a RED LED for the 5th LED in the VU meter might be confusing... maybe I should just change the 5th LED to Yellow instead of RED?
-
So that +17dB on the VU meter is still a good 5dB away from clipping.
EDIT: So I guess using a RED LED for the 5th LED in the VU meter might be confusing... maybe I should just change the 5th LED to Yellow instead of RED?
Would having 5 dB of headroom at the point the user starts to worry about gain be a bad thing? I am thinking most people everyone will be recording into digital recorders and any signal hot enough to light the +10 dB LED will be more than capable of delivering a clean level for a digital recorder to deal with?
What I am saying is 5 dB safety margin on an analog device that is aimed at recording mainly concert material (with unpredictable max volume) is probably a good thing. I know on my MixPre maxing the peak meter does not = audible distortion, but still keep well away from it.
digifish
-
Ideally, one should record at an average of 0dB analog (which corresponds to -18dbfs (or lower) on your digital scale A/D). Any peaks in the sound would be covered well by the analog headroom (where you have +18 to +22dBu above 0dBu, which then corresponds to 0dBFS on the digital scale), thus there is no danger of clipping the A/D.
If you record HOT that your average level is +10dBu, you run into clipping the AD more likely than someone recording at 0dBu average. (Because the former has 10dB less headroom to work with.)
Maybe this diagram would show what I mean.
(http://homestudioguide.com/content/binary/CalibrateDiagram.gif)
-
EDIT: So I guess using a RED LED for the 5th LED in the VU meter might be confusing... maybe I should just change the 5th LED to Yellow instead of RED?
I think you should keep with red, and that overall the green>yellow>red scheme will work great.
Not meaning to place this on O-canis, but I think there is some confusion on this board between dBu, which is simply a representation of voltage, and dBFS for digital recorders. That is, many know you cannot go above 0dbFS without digital clipping and therefore assume that something like 17dBu must be bad (when all it means is you are putting out a signal at a level of about 5.5v). The dBu output level of the preamp really only has meaning in regards to point at which the preamp can no longer provide output without distortion, and also the maximum level the ADC or recorder can accept without itself clipping.
The gain structure of the ADC/digital recorder creates a relationship between the dBu output of the preamp and dBFS of the digital recording, but there is no inherent relationship between dBu and dBFS (i.e., any relationship defined within the preamp itself).
-
Just for clarification... for the VU meter, the 5th LED denotes:
+17dBu = 5.48 Vrms = 15.51 Vpeak-to-peak
The preamp's max out is about
+22dBu = 9.7 Vrms = 27.5 Vpeak-to-peak
So even if the 5th LED lits up, the pre is still far away from actual clipping.
That said, nobody should be recording at +17dBu average... but it's okay to have peaks at that level. You want your signal chain setup just so when your pre is peaking (for loud material) at +17dBu or above, your A/D converter should just be showing maybe -3dB below the 0dBFS clipping point.
-
Excellent explanations guys +t
-
Just for clarification... for the VU meter, the 5th LED denotes:
+17dBu = 5.48 Vrms = 15.51 Vpeak-to-peak
The preamp's max out is about
+22dBu = 9.7 Vrms = 27.5 Vpeak-to-peak
So even if the 5th LED lits up, the pre is still far away from actual clipping.
That said, nobody should be recording at +17dBu average... but it's okay to have peaks at that level. You want your signal chain setup just so when your pre is peaking (for loud material) at +17dBu or above, your A/D converter should just be showing maybe -3dB below the 0dBFS clipping point.
Perhaps you could mill an analog to digital meter calibration table on the base of the unit :)
digifish
-
Shake, and Bake!
-
Mmmmm, chicken.
"And I helped"
-
Nothing exciting to show yet....
but making slow progress with it...
(http://farm4.static.flickr.com/3280/2640440211_5a0c0df367_o.jpg)
It's going to be tight... but everything still fits so far. 6" wide, 4" deep for the motherboard PCB. I wonder if I should switch to SMD parts.
Check out the 2 vertical VU meters. And we also got some transformer mojo going on here.
-
Nothing exciting to show yet....
but making slow progress with it...
(http://farm4.static.flickr.com/3280/2640440211_5a0c0df367_o.jpg)
It's going to be tight... but everything still fits so far. 6" wide, 4" deep for the motherboard PCB. I wonder if I should switch to SMD parts.
Check out the 2 vertical VU meters. And we also got some transformer mojo going on here.
Simply Awsome.......I bet the pre is going to sound amazing.........
Peace OOK
-
count me in for one 8)
-
What's it going to weigh with those transformers in there? We may have to come up with an appropriate nic name. "The brick" is already taken.
-
(http://farm4.static.flickr.com/3280/2640440211_5a0c0df367_o.jpg)
:hmmm: What are those funny round things that look like squat capacitators? ;D 8)
-
Flux capacitors...
-
back after a week away - still looking good
-
and all I need mine to be is able to handle 7.2v NIMH rc car batteries, have reliable On/Off Power Switch that wont easily eb bumped and the preamp turned OFF accidentally :( Altho that would be impossible in my Cairn II 8) And I need a reliable gain switch/control/knob/whatever :) I can handle trim/rest of gain on my 722's Line-In 8) And XLR In/Out :) And transformers, and thsoe LED's look PERFECT for our purposes as long as you configure them like us tapers would want them to, which Im sure you will since you have thus far, which is VERY KIND IMO. Thanks for ALL of your efforts and to listening to teh picky hobby that we do ;D 8)
So are those Cinemag transformers as high quality as the Jensen/Richenbacher ones ???
-
> So are those Cinemag transformers as high quality as the Jensen/Richenbacher ones ???
Personally, I like them. A lot of other pro audio companies are using Cinemag trafos too. You'd also find them used in some API clone pres.
I think they're just as good as the Jensens quality wise, at a lower price. Note that Jensen/Cinemag/Richenbach kinda all came from the same "DNA."
From the Cinemag website....
CineMag was founded in 1979 in North Hollywood, California. Its mission is to manufacture the very best audio magnetic components in the world. However, its history goes back to 1953 when its founder, Tom Reichenbach, was a youngster and was already making transformers with his father, Ed.
Edward Reichenbach's experience in the audio transformer business goes back to Altec Lansing during World War II. Starting there, he designed many transformers which ended up in their equipment. There are some interesting pictures of Ed at Altec Lansing on the Cork Board. After Ed left Altec Lansing he manufactured audio and power transformers and inductors on his own. Eventually, Ed formed Reichenbach Engineering and developed a line of transformers which became ubiquitous standards in the pro audio industry. Tom worked with Ed until 1979, when he formed CineMag. CineMag was originally located at Reichenbach Engineering, but after a few years outgrew the facility.
and all I need mine to be is able to handle 7.2v NIMH rc car batteries,
The pre will work with voltages even less than 7 Volts.... tested down to 6.5V. And using the Tekkeon battery, it still worked even with the voltage selector set to 4.5Volts. ( I didn't test phantom power at those low voltages though. )
have reliable On/Off Power Switch that wont easily eb bumped and the preamp turned OFF accidentally
I'm using toggle switch, with stainless steel lever. Separate On/off switch for the VU meter functions too.
And I need a reliable gain switch/control/knob/whatever
The 12-step Grayhill selector switch cost $18+ alone. These are the same Grayhill selector switches used in preamps costing $1500 and more!
The pot used is sealed, conductive plastic Bourns potentiometer. NOT carbon film that will fade and get worn out after a few use, or open to the elements.
And XLR In/Out
I'm using Neutrik XLR with locking connectors. NOT plastic.
Thanks for ALL of your efforts and to listening to teh picky hobby that we do
Thanks for your interest and feedback!
-
I love this thread
-
Just a little update: Finished doing the PCB design for half the board... ;D
(http://farm4.static.flickr.com/3142/2647432727_a0ac85e32a.jpg)
-
Totally fascinating to watch this develop on our little board!
-
Here, here ! 8)
-
It looks easy because it's still all "virtual" :)
Spent a couple of hours last night finishing the other half of the board. Looks good if I may say so... not a single jumper wire used.
(http://farm4.static.flickr.com/3114/2650321738_99320ccc18.jpg)
Now, I just need to do a final review. I may be able to send out both the motherboard and switchboard PCB later next week, and order some prototype PCBs.
-
Hmm, no updates in almost a week ??? Going through withdrawal ;D
-
sorry about that. :)
Update:
The files were sent to the factory on the 11th, been in email communication with PCB fabrication house to answer a few questions. I should have on my hands the real, actual PCBs for the motherboard and switchboard on the 23rd.... woohoo!
Gimme a few days to build one prototype... and we'll see how it goes.
Assuming I didn't make any mistake in the PCB design layout, it should work on the 1st try. Otherwise, there goes $350+ on bad prototype PCBs.
Continuing to do do listening tests on a product I've yet to release, has a nice big fat bottom end, silky smooth highs... also been testing the DC-DC PSU for several days now. Both technologies incorporated in the TS-2 design... so I'm confident the TS-2 preamp will work and sound good.
However, the TS-2 has one design change not in my original SC-1 preamp. Theoretically, it should not change the sound, should even make it more quiet and improve noise performance further. But since the mod is on the signal path, it will be interesting to hear the change (or not hear it.)
-
sorry about that. :)
Update:
The files were sent to the factory on the 11th, been in email communication with PCB fabrication house to answer a few questions. I should have on my hands the real, actual PCBs for the motherboard and switchboard on the 23rd.... woohoo!
Gimme a few days to build one prototype... and we'll see how it goes.
Assuming I didn't make any mistake in the PCB design layout, it should work on the 1st try. Otherwise, there goes $350+ on bad prototype PCBs.
Continuing to do do listening tests on a product I've yet to release, has a nice big fat bottom end, silky smooth highs... also been testing the DC-DC PSU for several days now. Both technologies incorporated in the TS-2 design... so I'm confident the TS-2 preamp will work and sound good.
However, the TS-2 has one design change not in my original SC-1 preamp. Theoretically, it should not change the sound, should even make it more quiet and improve noise performance further. But since the mod is on the signal path, it will be interesting to hear the change (or not hear it.)
fivefishdiy how do you do comparisons to listen for any change in sound when you make changes?
-
Easy.. It's very unscientific :)
The preamp out is connected directly to an 8" active monitor (bi-amp). I have to be careful that my distance to the monitor is the same for both tests. I'm usually sitting down, and I always look at the same reference point (say, a picture frame, or spot on the wall, or the tweeter cone). That way, my head position is always the same, and therefore my ears are at the same spot too (or roughly the same spot).
I have the stock pre, and the modified pre (or prototype) on my desk. First, use the 1st pre. I'll loop the same music material continuously, until I'm used to the sound. Then I'll switch jacks and run the 2nd pre... same material, same distance, same head position. I'll take note of specific musical passages, and keep looping it. Then I switch again and see if what I think I heard is really there, or just my imagination. I use orchestral music, with very fine piano passages, and loud percussive sound in other parts, mixed with some strings, french horns, etc in other passages. I'll take note of the crash cymbals or the taiko drum, or the violin strings. How do they sound.
I remember on an early preamp prototype last year, my pre would "trip up" when one specific section came up (very loud, very transient percussive sound) on one specific music (It was a Yanni CD ;D ) It didn't happen on any other loud music material or CD... just this one particular song. So hook up the oscilloscope, run the audio generator and sweep up and down the frequency until I replicated the problem. So that got fixed.
In another case, I noticed the output of the 2nd pre was lower in volume than the 1st pre. It seems just a tad bit lower, but hardly noticeable listening to it. So I hooked up an oscilloscope and measured it, and found the output of the other pre was 0.4V less. Reviewing the board, I noticed a 2K67 resistor instead of a 3K32 in it's place. Replaced it, hooked up the oscilloscope and now they're on the same volume, and listening tests confirm it too.
And I'll do the same listening tests several times, a few days apart also.
I also have a software spectrum analyzer just to see if anything changed... But it's really hard to tell because the graph doesn't tell the whole story. (Not unless the change is really obvious.)
Swapping chips with another model/brand can also reveal the weakness of the older chip models. The high frequencies just get smeared and harsh to the ear (sounds like a fissssssh instead of a pissssss) , and the music just sound lifeless and dead. It's like the difference between listening to a speaker covered with a blanket, and listening to one without. That's best how I can describe it, like a veil being lifted.
I also try different mics, dynamics, condenser and ribbons.
Sometimes, I'll record the same performance on 2 different signal paths, and then chop the resulting audio and butt them together alternately, and listen to it to see if there are differences. Here's an example:
http://www.fivefishstudios.com/audio/SC-1ActiveDI-vs-RadialActiveDI.mp3
Everytime you hear a click or tick, that's audio being swapped between the 2 sources. This is a comparison between my Active DI and a commercial $200 Active DI unit. The $200 DI has a tiny bit more low end than mine, but nobody would even notice it if not pointed out.
Anyways, I don't know if that answered your question but that's how I do things. Whether it's right or wrong, who knows? Each person will have their own ears, their own personal biases, etc... See the June 2008 issue of AES Journal about how personal bias affects listening tests. (factors like price, look, brand, equipment model#, and also mood, music preference, nationality, etc.)
-
No, you're right. PCB cad has Design Rule Check and Error Check tools. But I still make mistakes :) Human mistakes no software will catch.
Like in one job I did, I drew the schematic wrong. I connected one of the trace to the wrong junction. So the PCB design tool didn't catch it, because it was "correctly laid out". But electrically, it was wrong.
Another old mistake was putting the component backwards (i.e. a selector switch). The PCB design/layout was correct, but the component was backwards.
And another one was pulling up an LM317 regulator part instead of a 337 regulator part. The part looks the same, but the pin-outs were different. The PSU didn't work, and everything got hot :-[
Just dumb mistakes. It's the little ones that get you.
-
this thread rocks!
I look forward to this product.
-
UPDATED:
New prototype boards came in today... wohoo!
(http://farm4.static.flickr.com/3224/2696250717_538ea4129b_o.jpg)
Let's do some test fittings...
The (2) VU Meters
(http://farm4.static.flickr.com/3075/2696250865_7c0a8e0d37_o.jpg)
and oh yeah.... 2 input transformers.
(http://farm4.static.flickr.com/3045/2697065830_d5c7b51997_o.jpg)
This is the switchboard...
(http://farm4.static.flickr.com/3198/2696250991_b2b279b01b_o.jpg)
A preview of things to come...
(http://farm4.static.flickr.com/3178/2697065676_007817b174_o.jpg)
Next step: Build a prototype using these new boards and see if it works.
-
^^^
Nice. I love the way you integrated those VU meter boards into your mainboard. Very clean!
Richard
-
Next step: Build a prototype using these new boards and see if it works.
Truly impressive. Wish it were going to be portable size, I would be all over it then. Looks great though!
-
Next step: Build a prototype using these new boards and see if it works.
Truly impressive. Wish it were going to be portable size, I would be all over it then. Looks great though!
It is going to be portable sized... per the rest of this thread.
-
It is going to be portable sized... per the rest of this thread.
Okay, thanks for the info. I only read on the first page that it wasn't going to be very portable sized but haven't yet looked through the other 16 pages. Anyway, if it's going to be portable sized, then I really need to have one of these. 8)
-
i have no need for a preamp, i have a schoeps vms 5u, but this is the best thread i've read. i have followed this from day 1. it's been fun to follow the progress of this taperssection preamp.
+t fishfivediy
best of luck and welcome aboard.
ed
-
Built the TS-2 switchboard PCB, tested the 48V phantom power section and it works A.O.K!
LEDs will be mounted under the board.
I can already see a few minor changes to the board design... need to push the switches a bit more forward, maybe by 0.1"
The height clearance is perfect... about 1mm for the caps and about 2mm for the switches between these parts and the celing height of the case. Real tight...
Again, here's the initial design that existed only on the computer.
(http://farm4.static.flickr.com/3164/2608451055_17ff6990e9_o.jpg)
And here it is, in real life :) (with a few minor changes as you can see.)
(http://farm4.static.flickr.com/3144/2703527901_15433e5e03_o.jpg)
Now, off to build the main motherboard. ;D
-
Got pulled to steak grilling duties and making home made creme brulee's :)
Anyways... finally got some time tonight to do some work on the motherboard.
First, populated the PSU section to see if it works... yup, A.O.K. (had to jumper the switch temporarily since the motherboard isn't hooked to the switchboard.)
So far so good, the switchboard, 48V section, and now the DC-DC section are all working fine.
Work done so far... all resistors, zeners and diodes stuffed.
(http://farm4.static.flickr.com/3228/2705073075_844388bbdc_o.jpg)
Tomorrow after church service, I'll solder the caps, IC sockets, pots and switches and XLRs, then start testing.
-
You have a waiting list going?
:D ???
-
Finally finished one channel and did some testing.... THE MOMENT OF TRUTH is coming! Will it work or not???
Woohoooo!!!!! YES! ;D ;D ;D
At first I wasn't getting any signal and was in a bit of panic... I'm thinking "oh no... what did I do wrong?"
Told myself I need to calm down and re-check everything step by step. Found out I have a loose connection since everything is just temporarily affixed with tape and alligator clips. Secured that connection and now we have continuity.
Device Under Test
(http://farm4.static.flickr.com/3037/2708598786_a5db5d037b_o.jpg)
Then I heard music... coming from my signal source... YES! It works and passes signal. Sounds good too! Pretty stoked about it. Check the gain settings, it works... check the trim, it works. I tested it with a line level input and an SM57 dynamic mic, and yes, sounds great. I haven't tested it yet with condenser mics since I don't have the switchboard hooked up yet... (the switchboard has the 48V phantom power converter).
After an hour of music listening, hooked it up to my signal gen and oscilloscope to see out how things are.
Check it out... here's the square wave response at 1Khz. Notice how clean and sharp the square wave response is... no ringing, oscillations or instability at either the rising and falling edges!
Square Wave Response 1Khz
(http://farm4.static.flickr.com/3068/2707780857_5349d87c0c_o.jpg)
Did some output measurements while we're at it... how high an output can we go before clipping or instability. I'm not expecting it to be high (like +27/28dBu) since we're not using high supply voltages here, just a DC-DC converter PSU... but let's see what can we get...
Not bad.... not bad at all. Some readings....
15Hz @ 32Vpp = +23 dBu
20Hz @ 35.6Vpp = +24dBu
1Khz @ 37.7Vpp = +24.7 dBu
22Khz @ 31.1Vpp = +23dBu
100Khz @ 24.4Vpp = +20dBu
200Khz @ 14.65Vpp = +16.5dBu
Output waveform at 100Khz.
(http://farm4.static.flickr.com/3168/2707839339_13c6c2fe2e_o.jpg)
What's the Next Step?
Build the 2nd channel on the TS-2 preamp board, then test together the Motherboard and Switchboard...
Metalwork/CNC for the case, verify measurements and hole locations
So far, I'm pretty pleased with how everything is working out, from concept and design on paper, to CAD, to a working prototype.
-
Very cool stuff.
A lot of the technical details are lost on me (though I'm learning more every day) but I've really been enjoying this thread.
-
Well... a bit of bad news. :-\
This project was going smoother than normal, that it's very unusual. I was expecting problems and now I got it.
The VU meter boards are 0.2" too tall! They will need to be redesigned, and remanufactured and reduced in size to less than 1" height. Also, since they will always be vertically mounted, I don't need the jumpers and headers for configuring the change of direction movement of the LEDs. That should reduce cost too.
While fiddling with the board with power applied (i know, it's stupid), my metal XLR jack flopped over the board and caused some shorting. Now the on-board PSU is dead. And I don't have any replacement parts. That was my last part! Arrrgghh... Parts are on order but will probably not arrive until later this week, or early next. So my planned burn-in testing won't happen.
But here it is... the finished TS-2 preamp motherboard. From design to working prototype in 3 weeks.
(http://farm4.static.flickr.com/3114/2650321738_99320ccc18.jpg)
(http://farm4.static.flickr.com/3212/2708917151_a9b9f02c70_o.jpg)
So when you buy this pre, not only are you getting a high quality sound, but rest assured, you're also getting high quality components, parts, and build assembly inside the case. Even the stuff that people normally don't see, are important to me. "Simplicity Counts...Details Matter." If you open the case, I don't want to be embarrassed by what you'll find.
That's all for now... ;D
-
+T!
I know less than nothing about electronics, but this thread, the jpg's and your explanations have been instructive and entertaining at the same time. It's great to be able to watch something taken from an idea to a reality. Thanks!
-
looks very nice...can't wait to see it go to market :)
keep up the great work!!!
-
Very nice. I would certainly trust gear made by you, all that testing is excellent.
By the way, are you using THAT chips as line drivers for the output?
RIchard
-
Very nice. I would certainly trust gear made by you, all that testing is excellent.
By the way, are you using THAT chips as line drivers for the output?
Thanks!
Yes, those are THAT chips for the line output driver. These will drive 600-ohm loads without breaking a sweat.
UPDATE:
Here's the VU meter board (Rev1.1) mounted on the TS-2 motherboard.
(http://farm4.static.flickr.com/3093/2715190070_2ae96b6393_o.jpg)
As I said earlier, it was 0.2" too tall. So I had to do some relayout and bring it down to 1" height.... it's getting smaller and smaller, see photos below.
(http://farm4.static.flickr.com/3039/2714375717_5939f42656_o.jpg)
This means more $$$ expenses to remanufacture the new Rev1.2 boards. Bummer...
But no big deal, I can reuse the Rev1.1 boards and they'll be perfect for use with 1u rack cases.
If you're interested in VU meters for your audio projects, I also sell them as kits... $19 ea.
Let me know if you want the VU-1 or the VU-1B style.
- 5-LED VU
- wide supply range.. 4V to 24V. (on-board voltage regulation to +18V)
- You can change LED direction via jumper wires to allow for horizontal or vertical mounting.
- on-board trimmer for calibration
Watch a video of it in action.
http://www.fivefishstudios.com/video/VUMeter.mp4
Note:
The 5th LED on the VU meter lights up at +17dBu... but the pre can do at least +23dBu output (from 15Hz to 22Khz) before clipping... so you have a good 6dB buffer before actual clipping. That should be plenty enough margin for normal use. (At 100Khz, output before clipping goes down to +20dBu... still good 3dB margin... but who can hear 100Khz anyway? :) )
-
i dont want to jump the gun, but when do you think you will have pricing figured out?
-
jerryfreak
The metalwork is a big ? at the moment. I'm still deciding how the aluminum front panel should be finished.
So the answer to your question.... no definite price yet.
But rest assure I want this thing to sell... so I will surely price this reasonably and competitively.
O-Canis
There is nothing inside the aluminum case that generates a lot of heat so heat is not going to be a problem. It's not even going to get warm.
Heck, even the 110V/220V-powered rack preamps I make barely just get warm. So I'm not worried about heat problems on a 12VDC powered preamp.
-
+T Five Fish Man!! ;D
I've been waithing to get my 50 posts in so I could +T you on this thread!
I remember talking to you about this on your own forum. I'm so glad things are progressing here for the Tapers. I think your pre is going to be Da Bizness.
Maintaining the high gain with low noise, super clean performance in the portable version makes your TS-2 not only super versatile and flat out awesome, but also fit squarely into the nature recordists' niche.
I bow to your design sensibilities, Dude.
:fish::fish::fish::fish::fish:
Peace,
Sanaka
-
FiveFishdiy,
Do you have any idea when these will be available?
Are you still a couple months away from having a finished product for sale?
It looks near complete, but I am no expert.
-
Sanaka
Yeah, finally getting there... slowly.
GDfan : Are you still a couple months away from having a finished product for sale?
It looks near complete, but I am no expert.
That's a good guesstimate. Maybe even 3 mos.
There's no case work yet, the VU meter needs to be redone, and I usually build 2-3 prototypes to make sure it works.... EVERYTIME it's built. Also, haven't had a chance to totally burn-in the unit to see that no problems comes up.
-
Fivefish --
Now that the boards are in and the preamp is coming together, could you refresh our memories on what the features will be? I tried reading through the thread, but I'm not sure I found everything.
IIRC, it was something like 6db stepped gain, trim pot adjustment between the gain steps, separate 48v phantom selectable for each channel, phase reversal for each channel (mainly for the home recording types). Did you decide on having a high pass filter option? Battery requirements -- 9v or 12v, will 7.2v cells work?
This still looks very cool, great to see the progress!!
-
could you refresh our memories on what the features will be?
6db stepped gain
Yes.
trim pot adjustment between the gain steps,
Yes.
separate 48v phantom selectable for each channel,
Yes.
phase reversal for each channel (mainly for the home recording types).
Yes... POLARITY reverse. :)
Did you decide on having a high pass filter option?
No filtering. Mixed response here from tapers.
Battery requirements -- 9v or 12v, will 7.2v cells work?
Yes, Yes, Yes.
While the pre will still work down to 6.5Volts, I recommend 9-12VDC input. Max 14V.
Sidebar: I have the Tekkeon battery with the adjustable outputs. I remember that the pre worked on any setting between 4.5V to 14V. But I didn't test it with condenser mics. I should try that.
-
Re: highpass
Since some wanted it could be switched out of the path was it eliminated just to save space?
-
There were also other issues associated with it. Additional opamps, increased power consumption, cost, and the switches are on a separate board and I dont want LOW level signals jumping back and forth between the motherboard and switchboard.
If you want the signal filtered, it can be filtered during post processing, and you'd have better control of cutoff frequencies, Q factor, dB reduction, etc... during post. If the filtering is in the box, it's fixed and you cannot UNDO undo it later.
-
Tested the other channel on the preamp board... oh yeah... it works! :)
Now, time to do some burn-in testing.
BATTERY TESTING Part Deux...
Hooked up the 2-ch pre to a Tekkeon battery... run some music signal and listened to it on my monitors... everything connected using test clips. What's the current consumption of the preamp? (i.e. with the VU Meters turned off)
* You can see which LED is lit up on the Tekkeon battery which designates the output voltage selected.
TESTING AT 12VDC ... of course no surprise here, it will work
(http://farm4.static.flickr.com/3132/2721057440_1abe278b8d.jpg)
MAX voltage input is 14VDC...
(http://farm4.static.flickr.com/3157/2720233119_469e8a1449.jpg)
Okay, no surprises there...
Just for kicks... I decided to lower the input voltage to see how it holds up... At what point will the sound disappear and the pre stops working?
Let's try 9Volts... still works.
(http://farm4.static.flickr.com/3138/2720233321_157cd14879.jpg)
How about 6Volts... surely it will drop at 6Volts... but nope, it's still working.
(http://farm4.static.flickr.com/3100/2720233275_19b2455e4a.jpg)
This is disappointing... ;D Let's try 4.5Volts input... That should kill it!
(http://farm4.static.flickr.com/3172/2720233227_5a1d73477f.jpg)
Nope... still working...
Okay, the lowest setting on the Tekkeon battery is 3 Volts... let's kill this pre, die die die.
(http://farm3.static.flickr.com/2063/2720233179_14f766d5a1.jpg)
Unfortunately, it's still working. Sound is still coming out of the pre. I've been listening for the past half-hour with the pre running on 3Volts from the battery and no problemo. It's still going.
Nothing feels hot. Not the battery, not the preamp, not the various chips, not the PSU section. Everything is C.o.o.l!
Sooooo, you can say I'm pretty pleased about the results.
PS: Notice my new multimeter? Yep... It's a Fluke, baby ;D
PPS: I'm not recommeding running it at a too low voltage like 3Volts, because that will affect your headroom (lowers your available headroom... most obvious when you have a thumping bass or low frequencies in your signal.) 4.5Volts is still good though :)
-
This is way cool! +T, of course.
How do you explain for the EE challenged the low voltage needed to run it?
-
Current draw on the battery must increase as voltage supply decreases, no?
Normally yes, current should increase as voltage decreases. That's the normal behavior I had with the 9V Duracell testing.
What part of your circuit are you measuring current? After the DC converter, I presume?
No, The figures shown above is the current draw from the DC supply (i.e. from the battery, before the DC converter).
I am surprised by the current readings too... the only thing I can think of is the Tekkeon battery has internal electronics in it (an adjustable boost converter?), and is not a straight battery.
Oops, forgot to answer this one.
How do you explain for the EE challenged the low voltage needed to run it?
The answers are the chips I'm using run on a wide range of voltages. Then using a DC converter, it's possible to "step-up" the input voltage from something low to a higher voltage... sufficient to operate the chips.
-
I haven't posted here, but I have been watching. Awesome to see something go from concept to reality. Your battery test, is that with full 48v load on it? I only see 1 XLR connected in the top left.
-
No, I don't have the switchboard connected yet to the motherboard in the above tests.
(The 48V supply is on the switchboard PCB.) I'll do another battery test with the whole shebang running.
But on an earlier test, these are the numbers I got, 2 channels loaded with FET condenser mics and 48V phantom.
2 Channels, with +48V phantom power, loaded with mics, plus VU Meters = 170mA - 190mA
The current consumption varies... depends on how many LEDs were lit up in the VU meters.
-
100-200 mA at 6V? you gotta be kidding me.
Bravo!
when you gonna add an a>d stage? ;)
-
Nothing much happening... awaiting some cable assemblies that I'd like to use with the TS-2 prototype. It should be here tomorrow.
Meanwhile, I found out a customer of mine from Netherlands made this recording. With his permission, it's posted on my website. The setup is just a pair of Oktava mk012 cardiod Microphones in a (10 x 18ft) room and 2-channels SC-1 Preamp recorded into a Yamaha AW1600.
It's a simple live recording setup and I thought you guys may be interested to hear it since it's similar to a tapers setup.
Full credits here:
http://fivefishstudios.com/index.php?option=com_content&task=view&id=17&Itemid=48
Audio file:
http://www.fivefishstudios.com/audio/without_Jean.mp3
The TS-2 preamp is based on this same SC-1 preamp, but with the addition of input transformers and an additional buffer stage. This should give you a close idea of how the TS-2 sounds and I think the TS-2 will sound even better due to the input trafos. (Other sample SC-1 recordings can be heard on the above webpage too.)
-
Mighty sweet indeed ;D
Peace
-
Update:
My wires arrived today... yay!
I got the switchboard and motherboard working together... Schweeet!!!
I haven't wired the phantom power yet, and of course, the VU meters don't fit.... new VU meter boards will be here next week. But doing tests with a meter, all parts are functioning. (48V for phantom and 12V supply for VU). Phase reverse works too... if you toggle the switch to the middle, it's a mute (unintended consequence).
I also need to solder the mini-LEDs for the switchboard...
(http://farm4.static.flickr.com/3220/2736975358_90a1b08bd6_o.jpg)
OF COURSE!... I had a stupid mistake on the board. Nothing major... but the output jacks are swapped.
So it's like
IN1, IN2, OUT2, OUT1
instead of
IN1, IN2, OUT1, OUT2
Will fix this on the next board revision. The important thing is everything is working.
-
Sweet torture ...
...I want one NOW!
>:D
-
Update:
My wires arrived today... yay!
Nice! I notice you must have the highest +T to post ratio of any Taperssection user, currently @ ~2:1 :)
I forget what the power supply options will be. However it would be nice if you could make a AA battery sled for it. 8 AA batteries?
digifish
-
Nice! I notice you must have the highest +T to post ratio of any Taperssection user, currently @ ~2:1 Smiley
Hehehe... I try not to post too much. It keeps my signal to noise ratio high. ;D
However it would be nice if you could make a AA battery sled for it. 8 AA batteries?
8 batteries? I think (3) will work... 4.5Volts.
I have 1" extra real estate in the case. But no promises. Changing out batteries will be a pain. Not unless I can find an easy method for access. It probably wouldn't happen... but hey, I love a good challenge.
I forget what the power supply options will be.
In the original design, I used 12VDC input as my design criteria. But after the prototype preamp was built and tested, I found out it will work down to 4.5VDC input just fine.
HOWEVER... the Phantom power will not reach a full 48Volts if the pre is only given 4.5VDC input. This may or may not be an issue for you. If you're using dynamic mics, who cares. If you're using a typical condenser, it should work even with PP of 12V or 15V or 18V. A certain few types of condenser mics though prefer a higher voltage and sound crap at a low phantom power voltage. I use a FET condenser mic as my test mic. This mic is picky with regards to phantom power. So if it will work even at 4.5V input to the preamp, I'll be happy.
Here's the table of input DC voltage and the phantom power voltage you'll have available at that corresponding voltage.
(Phantom voltages rounded up or down to nearest value.)
Battery voltage = Phantom power voltage available
----------------------------------------------------------
4.5V input = 28V phantom <---- Not bad for phantom power even at 4.5VDC input
5.0V input = 32V phantom
6.0V input = 41V phantom
7.5V input = 48V phantom <--- at 7.5VDC input and above, we get full 48V phantom
8.0V input = 48V phantom
9.0V input = 48V phantom
12V input = 48V phantom
14V input = 48V phantom
So there... since PP specs are 12V to 52V range, I *think* it won't be an issue. 28Volts is more than twice the minimum 12V spec. Once I get PP wired, I will do some real world testing with my FET condenser mic.
More pics...
Front View... I need to get proper 1" standoffs.
(http://farm4.static.flickr.com/3198/2737016531_f2fc4e64c4_o.jpg)
Wiring closeup... I'm using headers to simplify and speedup assembly. You can see at the lower right corner of the PCB some pads for hooking up Switchcraft locking DC jacks.
The DC inputs are protected with diodes too! So no danger of hooking up your battery backwards! I think that piece of mind is worth the $0.05 the diodes cost me ;D
(http://farm4.static.flickr.com/3036/2737852724_de7c56b674_o.jpg)
-
Nice! I notice you must have the highest +T to post ratio of any Taperssection user, currently @ ~2:1 Smiley
Hehehe... I try not to post too much. It keeps my signal to noise ratio high. ;D
However it would be nice if you could make a AA battery sled for it. 8 AA batteries?
8 batteries? I think (3) will work... 4.5Volts.
Thanks, I was thinking of running it at 6V but with 8 batteries for more serious mah. Just that AA batteries are everywhere, easy to manage and everything I own runs on them :)
digifish
-
Well, my LUCK ran out.... Murphy's Law strikes again!
Found a major mistake.... at the very last step!
So I wired the phantom power wires from the switchboard to the motherboard... then problems... I'm not detecting any phantom power on the XLR jacks.... Guess what? I connected the phantom power resistors on the wrong side of the input transformers on the motherboard! What a stupid mistake! I drew it wrong in the schematic. And of course, since I don't have a second set of eyes checking my work, it slipped through.
It's not a complete show stopper... I'd just have to solder the resistors at the bottom of the board and use some jumpers.
Soldered the (3) LEDs to the switchboard.... The 3rd LED (Power LED) wouldn't light up. I think I overheated it. The (2) phantom power LED indicators are working fine though.
I'm calling it a day... just when I'm at 99% complete, I'm making stupid, simple mistakes.
-
dear fivefishdiy:
First off, congratulations on such a fantastic design project and what's turning out to be a model success story for a product that's custom tailored to the target market. How better to do it than you are? I'll buy one of your preamps for that reason alone!
I've read the input here and there as it's gone along, but I'm not really tech saavy enough to provide much input. However, just today I spent that last three hours really reading and absorbing everything that's been offered up to this point. I hope you don't mind at this late stage some new eyes on this project and maybe a couple of new thoughts...take the input for what it's worth and it's probaby too late to matter. However, I do have some input that might be useful.
I have an Apogee Mini-MP preamp that I recently inadvertently toasted because I accidently applied reverse polarity to the power jack. Actually, I am thinking (based on other threads that I've read on this same subject related to this preamp) that the whole preamp isn't cooked, but probably just an internal fuse that is located at the output jack as reverse polarity protection. I don't know circuit design, but on the one hand, I'm glad that I probably have only a blown fuse. However, on the other hand, my preamp is now DOA until I have it serviced which of course is a PITA.
For pretty much every other electrical component I own, if reverse polarity is applied, the only thing that happens is...well, nothing. In other words, the component doesn't power on, but it also doesn't fail. So, maybe the fuse is an additional form of reverse polarity protection on the Mini-MP (in addition to a diode), but FWIW I don't like it because I still have a dead preamp.
So, I guess my input is:
a) make sure that your preamp is fully reverse polarity protected (you mentioned output diodes, so I guess you have that covered???), and
b) make the design respond passively if reverse polarity _IS_ applied. Yeah the fuse might be an additional form of protection, but now that it blew, I still have a dead preamp that's gonna cost me $100 to get fixed by Apogee, so from my perspective, I'm not sure what's been saved with this design.
Of course, your final case design should indicate in the cover artwork at the power input what are the polarity and voltage requirements are...surprisingly, a good number of my electrical gadgets don't give polarity requirements at the jack.
A second input on the case design is that I REALLY like the idea of standoffs at the rear of the unit, but I understand and agree with your efforts at permanent installation and how they are be in the way. A thought I had when I saw your pics was some sort of removable or screw-on standoffs. Or maybe some brackets or something that's kinda 'C' shaped and snaps onto the back with some detents to snap into place. Or maybe a bracket that swivels out of the way...say it swivels flush to the sides of the preamp when not in use, but then swivels out around the back so that it acts as a stand-off.
Of course the goal of the stand-offs would be something that doesn't get in the way, but something that would provide stress relief on everything in the back (not only stress relief but 'movement' relief in the case of battery connectors becoming accidently disconnected) while also allowing the preamp sit in a gig-bag with the face upward so we can see easily see the lights and settings. Of couse the problem with 100% of existing preamps is that in that position, everything is resting on the wires or the RA plug of the XLR.
Regardless, of my input, congratulations on the great job you've done. Sorry for the latest mishap with board design, but from the looks of it, you're WELL on your way to having the one of the most significant success stories in net history (as for as TS.com is concerned anyway!).
-
Well, my LUCK ran out.... Murphy's Law strikes again!
BTW, I think that getting this far with so little going wrong is an INCREDIBLE feat and testament to simply excellent planning and such a careful, thoughtful and professional approach that you've used. The fact that Murphy has waited this long to strike is simply the reality that nobody is immune to Murphys dastardly ways.
Also, FWIW, I hope you still plan on using the vintage dial type knobs instead of the black ones in the pics at the top of this page. It wouldn't be a big deal if they ended up being the blackies, but those vintage knobs are COOOL!
OH, as long as I'm rambling...it would be excellent if your end product had external artwork that doesn't wear off over time...or is maybe even lightly etched onto the aluminum case using your CNC machine...or maybe a combination.
-
Sorry I keep adding onto this thread, but like I said earlier, I read on this thread for a LOOOONG time earlier today so I keep comging back to things that I read along the way.
Back a few pages there was some discussion about noise when the Tekkeon battery was sitting on the top of the box. FWIW, I read the following message a couple days ago...it took me awhile to find it, but I _KNEW_ I had just read on that subject. Check the link...not a whole lot of detail, but seems to confirm that your noise issue was simply an issue with having the Tekkon battery in close prox to your preamp...
http://taperssection.com/index.php/topic,97621.msg1443192.html#msg1443192
-
So, I guess my input is:a) make sure that your preamp is fully reverse polarity protected (you mentioned output diodes, so I guess you have that covered???),
Yes, I have protection diodes on the DC input jack to protect against reverse polarity.
(Not to be confused with the diode protection I also have at the output XLRs, which is meant to protect my pre when for example you plugged the outputs of my pre to the inputs of another pre/console by mistake and turned on 48V phantom on the other pre, which then goes to my pre via the backend. Of course, this scenario wouldn't happen to tapers but more likely for someone in a studio.)
(And not to be confused also with the input diodes on my pre, meant to clamp down high input voltages (example: 48V discharge) that may damage the pre.)
I just did a quick check with my bench PSU powering the preamp both with correct and reverse polarity voltages, and going back to correct polarity.
No problems. Dead as a doornail when reverse polarity powered.
Comes back to life when correct polarity is applied.
Just don't apply a reverse polarity greater than 400VDC. Otherwise, all bets are off. That's the max. limit. ;D
b) make the design respond passively if reverse polarity _IS_ applied. Yeah the fuse might be an additional form of protection, but now that it blew, I still have a dead preamp that's gonna cost me $100 to get fixed by Apogee, so from my perspective, I'm not sure what's been saved with this design.
You know of course with my DC input protection, I'm losing $100 everytime someone applied reverse polarity and NOTHING happens to my pre. ;D
A fuse is not meant for polarity protection but for current overload protection. If the current flowing exceeds the rating of the fuse, the fuse opens up. For example, there is a short inside the unit, you apply power, instead of the external PSU being damaged because of a short in the load, the unit fuse opens up. It's not a form of reverse polarity protection. A fuse doesn't care which way the current goes.
final case design should indicate in the cover artwork at the power input what are the polarity and voltage requirements are...surprisingly, a good number of my electrical gadgets don't give polarity requirements at the jack.
From a cost standpoint, (remember, I'm a very tiny small operation not a huge manufacturer with deep pockets)... that's one more expense for silkscreening or engraving the backplate. Maybe I'll put a metal sticker.
A second input on the case design is that I REALLY like the idea of standoffs at the rear of the unit,
You mean the bracket I installed in the back?
If the user is using straight XLRs, they do not get in the way. But the straight XLR is still longer than the bracket. So the bracket is useless.
If I put in a rear bracket, and somebody tries to use a right angle XLR, the brackets get in the way... and again, the right angle XLR is still taller than the brackets so the XLRs provide stress relief for the DC plug. So the bracket is kinda useless.
The only time the rear brackets provide stress relief is if you don't have XLR jacks plugged into the back, and only the DC plug. But who uses a unit like that? i.e. DC plugged in, but the XLR jacks not plugged in?
I will be using DC locking jacks, so there is no danger of the DC plug falling out. And if you use straight or rt-angle XLR jacks, they will provide stress relief to the DC plug. Somebody also mentioned locking right-angle DC plugs. That would be even better.
I hope you still plan on using the vintage dial type knobs instead of the black ones in the pics at the top of this page. It wouldn't be a big deal if they ended up being the blackies, but those vintage knobs are COOOL!
Yes, I agree! They are cool looking. I like them. Either way, the knobs will be easy to replace. I could offer both styles as an option.
Thanks for your inputs. Much appreciated.
-
Your preamp looks really good.. I like the vintage neve style knobs :) Anyway you should be very proud of it it looks sweet. One comment maybe instead of using jumper wires to go from board to board you can once you get into production use a pin socket system much better and more reliable.
http://www.erni.com/DB/PDF/STL-BUL/ERNI-PinHeader-Socket-e.pdf
-
One comment maybe instead of using jumper wires to go from board to board you can once you get into production use a pin socket system much better and more reliable.
Thanks Chris.
I've been looking at something similar. Mill-Max, etc... Some of them do cost a lot (but I guess that's recovered in the labor savings), and I'll need a free common area on both the top PCB and bottom PCB so the two will mate/align. The nice things about those Erni ones is it's ability to bridge a 1" distance board-to-board.
Ive seen blue and red cases. Is color of the enclosure at all something that can be selected on order without undue extra expense? I'm thinking dark grey or black might have appeal... and the Busman folks would want school bus yellow of course.
The enclosure itself is untouched. Only the front and rear panels will need to be machined. So I guess you can have a red case with black panels, or black case with red panels. I have not totally decided on case color... but for sure, I'm not leaning towards black. I have too many black stuff already... not unless the market really wants black.
-
Is color of the enclosure at all something that can be selected on order without undue extra expense? I'm thinking dark grey or black might have appeal... and the Busman folks would want school bus yellow of course.
Nextel Grey! ;D
-
One comment maybe instead of using jumper wires to go from board to board you can once you get into production use a pin socket system much better and more reliable.
Thanks Chris.
I've been looking at something similar. Mill-Max, etc... Some of them do cost a lot (but I guess that's recovered in the labor savings), and I'll need a free common area on both the top PCB and bottom PCB so the two will mate/align. The nice things about those Erni ones is it's ability to bridge a 1" distance board-to-board.
Ive seen blue and red cases. Is color of the enclosure at all something that can be selected on order without undue extra expense? I'm thinking dark grey or black might have appeal... and the Busman folks would want school bus yellow of course.
The enclosure itself is untouched. Only the front and rear panels will need to be machined. So I guess you can have a red case with black panels, or black case with red panels. I have not totally decided on case color... but for sure, I'm not leaning towards black. I have too many black stuff already... not unless the market really wants black.
Getting custom colors is very expensive. Unless you can buy say 50 cases and take them to get powder coated... I would really decide on a color and stick with it. Because in the end I think you will find keeping all the colors in stock to keep everyone happy is very expensive. I use Hammond boxes my self they are well made and reasonably priced and always in stock. I have seen some pin connectors in the digikey catalog that were pretty well priced. Its more money then wire for sure but in the end its faster to assemble no wires to strip.
Chris
-
Yes, I have protection diodes on the DC input jack to protect against reverse polarity.
(Not to be confused with the diode protection I also have at the output XLRs, which is meant to protect my pre when for example you plugged the outputs of my pre to the inputs of another pre/console by mistake and turned on 48V phantom on the other pre, which then goes to my pre via the backend. Of course, this scenario wouldn't happen to tapers but more likely for someone in a studio.)
Actually it is highly likely if someone is using your pre with an Erirol R44 or other recorder with phantom (Fostex, Marantz etc).
BTW: What happens if I short XLR output pins 1 & 3 (I know my MixPre would not like this as it has an active balanced output)...
(http://www.marketworks.com/hi/71/71133/yxf-247pinout.jpg)
digifish
-
Actually it is highly likely if someone is using your pre with an Erirol R44 or other recorder with phantom (Fostex, Marantz etc).
Oh okay... good to know. Either way, our backend is covered :)
BTW: What happens if I short XLR output pins 1 & 3 (I know my MixPre would not like this as it has an active balanced output)...
Like when you connect to an unbalanced input? No problemo. The drivers I'm using, according to the manufacturer, "uses a dual feedback-loop design that prevents the excessive ground currents typical of cross-coupled output stages (CCOS) when clipping into single-ended loads."
I've shorted these outputs accidentally during the course of my working with my SC-1 pre, and have not had any driver failures...
But if you read Rane Notes interconnection guide, use pins 2 and 3 when hooking up to unbalanced inputs. That's the recommended method... rather than shorting 1 and 3 and using both as gnd and pin 2 as the positive. You get better signal if you use pins 2 and 3 to connect to your unbalanced inputs.
UPDATE:
Finally fixed the phantom power error on my PCB design. I soldered the (2) 6.8K resistors on the bottom of the PCB and it was just a short bridge to the trafo inputs. It's a kludge, but it works. :)
(http://farm4.static.flickr.com/3290/2739560703_4d52dab28e_o.jpg)
OKAY.... did some testing... connected my power hungry FET condenser mic, set the battery to 4.5Volts and no go... my FET mic wouldn't come alive... 28V phantom power is not enough for my FET mic. I can hear a tiny faint signal, but no go.
Set the battery to 5.0Volts, turned on phantom power and IT'S ALIVE. The FET mic works! Nice and clear.... 6.0Volts and higher, and it's smooth sailing.
Note: Less power hungry condenser mics will work with 4.5VDC input to the pre.
SOFT START PHANTOM POWER
I can't remember if I mentioned this but my preamp is equipped with "soft-start" phantom power. Normally, when you turn on phantom power, 48volts is suddenly applied, full ON, in a split-instant, to your expensive mics. And you hear a big THUMP/THUD on your speakers.
Instead with my soft start phantom power, 48volts is gradually applied to your expensive mics. Like this:
(http://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Series_RC_capacitor_voltage.svg/720px-Series_RC_capacitor_voltage.svg.png)
Depending on your condenser mic, it may take 2-3 seconds for it to come alive... and you also don't get that nasty popping/thumping/thudding sound.
BTW... tested this preamp with my FET mic... Ooooohhhhh WOW! It's thick and phat, very solid lows but the high frequencies are still clear. I really really like it.
-
Oh yeah... I forgot to mention...
We now have pretty lights.
(http://farm4.static.flickr.com/3208/2739648465_ccfed0e4b4_o.jpg)
-
OH MY GOD, IT'S ALIVE!!!!! IT'S ALIVE!!!!!!!!!
-
BTW: What happens if I short XLR output pins 1 & 3 (I know my MixPre would not like this as it has an active balanced output)...
Like when you connect to an unbalanced input? No problemo. The drivers I'm using, according to the manufacturer, "uses a dual feedback-loop design that prevents the excessive ground currents typical of cross-coupled output stages (CCOS) when clipping into single-ended loads."
I've shorted these outputs accidentally during the course of my working with my SC-1 pre, and have not had any driver failures...
But if you read Rane Notes interconnection guide, use pins 2 and 3 when hooking up to unbalanced inputs. That's the recommended method... rather than shorting 1 and 3 and using both as gnd and pin 2 as the positive. You get better signal if you use pins 2 and 3 to connect to your unbalanced inputs.
Great thanks for the follow-up. Nice touch with the soft-start phantom too. So it will sizzle-in rather than thump :)
digifish
-
So it will sizzle-in rather than thump
Yup... 48Volt fantom phizzle shizzle.
Wha-cha gonna do with all that junk, all that thump.
No thump, no thump in my lovely pre-amp.
:)
-
I want it I want it I WANT IT~!
-
WOW! Can't wait to get my hands on the real thing.
-
Blue pre w/ lights! me like ;D ed
-
I'm 50 years old, but I'm damn well 100% sure if I'd have been doing this project, I'd have pee'ed my pants at the moment of truth!
-
I'm 50 years old, but I'm damn well 100% sure if I'd have been doing this project, I'd have pee'ed my pants at the moment of truth!
:yack:
-
Carry on, can't wait to have the opportunity to buy this.
Ditto - I'm looking forward to this Fall / Winter arrival on my doorstep...
:headphones:
-
Just doing some abuse testing... hitting and tapping it with a pen while turned on, dropping it with phantom power ON, etc... just to see if any problem comes up.
(PLEASE NOTE: I'm NOT suggesting you treat the pre with abuse.)
I think I found one issue.... mainly on the phantom power DC-DC section. I need to remove anything "mechanical" in the PSU section that is prone to minute vibration... so the IC sockets will have to go. It's causing some "popping" sounds when PP is on, and the PSU/board is tapped/dropped. (The IC sockets just rely on mechanical pressure/force to make contact with the IC chip's legs.) ... the trimmers seems to be just fine... so they'll stay for now... I think.
The popping sound doesn't happen if PP is OFF. So I know the problem is caused by something in the 48V PSU.
I'll build a second prototype of the switchboard and test my theory. This may delay launch of the pre. How long? I don't know. We'll see how the new testing goes.
Sorry for the delay....
-
Weird... I guess I hammered down that chip so much into the IC sockets, now it's not causing any popping sound anymore.
-
Weird... I guess I hammered down that chip so much into the IC sockets, now it's not causing any popping sound anymore.
Cool.
I'd like to have the option to swap out IC's.
-
I'm not talking about the preamp chips.... The preamp chips will remain socketed. (But I'm using da best in da bizness... why replace the chips :)
I was talking about the DC-DC converter chips causing the popping sound when phantom power is ON.
-
I'm not talking about the preamp chips.... The preamp chips will remain socketed. (But I'm using da best in da bizness... why replace the chips :)
I was talking about the DC-DC converter chips causing the popping sound when phantom power is ON.
Ah... OK..
I was just thinking that the best chips in the business today, may not be the best in a few years. For example, The INA217 replaced the SSM2017. There's lot's of debate here over the sonic differences between various op-amps and/or instrumentation amps. Some resourceful guys have made a living out of replacing stock components, op-amps for example, with different op-amps, in audio gear.
-
Just doing some abuse testing... hitting and tapping it with a pen while turned on, dropping it with phantom power ON, etc... just to see if any problem comes up.
(PLEASE NOTE: I'm NOT suggesting you treat the pre with abuse.)
I think I found one issue.... mainly on the phantom power DC-DC section. I need to remove anything "mechanical" in the PSU section that is prone to minute vibration... so the IC sockets will have to go. It's causing some "popping" sounds when PP is on, and the PSU/board is tapped/dropped. (The IC sockets just rely on mechanical pressure/force to make contact with the IC chip's legs.) ... the trimmers seems to be just fine... so they'll stay for now... I think.
The popping sound doesn't happen if PP is OFF. So I know the problem is caused by something in the 48V PSU.
I'll build a second prototype of the switchboard and test my theory. This may delay launch of the pre. How long? I don't know. We'll see how the new testing goes.
Sorry for the delay....
Use these machined sockets for your chips you will not have any issues.
http://www.king-cart.com/phoenixent/product=SOCKETS+DIP+IC+MACHINED/exact_match=exact
-
I'm already using those kind of sockets. Thanks.
Still looking at the weird problem. I'm beginning to think it's not caused by the PSU. I think it's related to the phantom power wiring fix I did.
-
I'm already using those kind of sockets. Thanks.
Still looking at the weird problem. I'm beginning to think it's not caused by the PSU. I think it's related to the phantom power wiring fix I did.
Yes it might be somehow your resistors are becoming microphonic... Try a bit of hot glue on them to dampen them to your circuit board.
Chris
-
I'm already using those kind of sockets. Thanks.
Still looking at the weird problem. I'm beginning to think it's not caused by the PSU. I think it's related to the phantom power wiring fix I did.
Yes it might be somehow your resistors are becoming microphonic... Try a bit of hot glue on them to dampen them to your circuit board.
Chris
Capacitors are more likely to be microphonic than resistors, but you're right. Parts can be microphonic and the usual way of dealing with it is to glue them to the rest of the circuit so that the whole thing moves together.
-
There's nothing microphonic about this preamp. This is all solid state, not toobs.
And no need to hot glue anything. I don't do that.
Now, certain ceramic capacitors in SMD format can have piezoelectric effect that can be heard as popping noise when dropped but I'm not using SMD parts but all PTH parts. PTH parts don't have this capacitor piezo problem (the legs absorb the vibration... but not the same case with SMD parts).
So I repeat... it's not MICROPHONIC noise or something.
I think I know what the problem is (and it's only happening on one channel and not the other)... but haven't got some free time to test my solution yet.... I'm swamped packing, filling up orders this past week and finishing a media website for the Olympics coverage. (I have a real job, this electronics business is just a sideline.)
We'll get to the bottom of it. :)
-
There's nothing microphonic about this preamp. This is all solid state, not toobs.
And no need to hot glue anything. I don't do that.
Now, certain ceramic capacitors in SMD format can have piezoelectric effect that can be heard as popping noise when dropped but I'm not using SMD parts but all PTH parts. PTH parts don't have this capacitor piezo problem (the legs absorb the vibration... but not the same case with SMD parts).
So I repeat... it's not MICROPHONIC noise or something.
I think I know what the problem is (and it's only happening on one channel and not the other)... but haven't got some free time to test my solution yet.... I'm swamped packing, filling up orders this past week and finishing a media website for the Olympics coverage. (I have a real job, this electronics business is just a sideline.)
We'll get to the bottom of it. :)
Electronics do not have to have tubes to have a problem with microphonics. I am sure you will get to the bottom of it. ;)
"Microphonics describes the phenomenon where certain components in electronic devices transform mechanical vibrations into an undesired electrical signal (noise). The term is derived by analogy to older microphones where that behavior is inherent in the design, while with modern electronics it is sometimes an intentionally added effect.
When electronic equipment was built using vacuum tubes, microphonics used to be a very serious design problem. The charged elements in the vacuum tubes would vibrate and the motion would change the distance between the elements, producing charge flows in and out of the tube in a manner identical to a capacitor microphone. A system sufficiently susceptible to microphonics could experience feedback.
With the advent of solid state electronics (transistors), this major source of microphonics was eliminated but smaller sources still remain. The ceramic dielectrics used in high-K capacitors ("Z5U" and "X7R") are piezoelectric and will directly transform mechanical vibration into a voltage in exactly the same fashion as a ceramic microphone. Wiring and cables can also exhibit microphonics as charged conductors move around and various materials can develop triboelectric ("static") charges that couple to the electronic circuits.
The sound of guitar amplifiers that incorporate the electronic chassis into the same cabinet as the speaker are susceptible to microphonics. Though a guitar amplifier's microphonics distortion is sometimes appreciated as part of the "special sound" of a guitar amplifier, a faulty vacuum tube or other component can cause out of control feedback. Unwanted microphonics-related audible distortions can often be alleviated by using commercially available vacuum tube dampers"
-
I'm sure it's not microphonics, since it only happens when Phantom Power is ON and only on one of the channel. With PP off, it's normal...
The other channel is behaving normally with either PP on or off.
if it's microphonics related, it will be happening on both channels, with either PP on or off.
-
Okay, I had a couple of hours free time this afternoon and worked on the prototype.
Mystery solved.
I found out it was two separate issues... and both issues were on the same channel!
One channel was kinda like "superchannel" and was immune from all these stupid problems. The other channel was like a problem child on crack. <shrug>
1. Because of my original error in drawing the schematic (and thus the error on the PCB design), and trying to jury-rig a solution, etc... etc... well... that kludge solution worked for the superchannel but it didn't work on the crack channel. Weird. Don't ask me... I don't know why. The 2nd problem channel doesn't have a reliable startup of it's phantom power. Sometimes there is PP, sometimes not.
So this time, I really fixed the wiring by doing it the way it's supposed to be in the schematics. YES! It now works reliably, and there is 48V phantom power reliably on both channels, everytime. The DC-DC converter sounds happy too (which was a clue for me), and the DC waveform on the oscilloscope looks way way much better.... the way I expected it.
2. POPPING SOUND. Another mystery that only happens on the crack channel. The DC-DC converter was just fine. As I said, it's not microphonics. And no need to hot-glue anything. Don't want that ugly stuff on my board. :)
The problem was the BurrBrown chip which I'm using as a DC servo. (yeah, my pre has no capacitor in the signal path between the mic preamp and the output driver... I'm using a DC servo). I guess this particular chip is marginal because as soon as I replaced it, everything was quiet and back to normal again. Tapping the board, and dropping it from 1 to 1.5" on the table was just fine. No loud popping sound, followed by some crackling noise. Sounds great!
So now, the prodigal son, errr... channel has come back to the fold and everything is working fine again.
I'll continue monitoring in the next few days to see if any new problem is discovered.
BTW.... running the pre on 5.0VDC input using the Tekkeon battery and with phantom power ON...and IT WORKS, my power-hungry FET condenser is happy and working. I'm very pleased with that.
-
Just reread this whole thread again, and am more jazzed than ever about this project.
Just a couple quick Q's for the 5Fish man :) :
- Will you fix the phantom resistor location problem on a new PCB revision? I assume so because you've emphasized that you usually go through several board revisions before releasing a project officially, but I didn't see where you mentioned it specifically regarding this problem. I feel a little bad asking, because I know it means junking a bunch of otherwise good boards...
- Have you settled on a definite set of uses for the 6 switches/positions? Sorry I missed it if you have. Do you have a photo of the face with the toggles instead of the pushbuttons? Like a couple others did, I'm doing my own (possibly annoying to you, sorry!) Photoshop mockup of the TS-2 front faceplate.
Peace,
Sanaka
-
I assume so because you've emphasized that you usually go through several board revisions before releasing a project officially, but I didn't see where you mentioned it specifically regarding this problem.
Yes, there'll be new PCB revisions. I already have some of the changes done in CAD for the 2nd PCB revision... about 12 or so items before I discovered the PP resistors error. The rest of the PCB design is good. I think these boards (rev 1) can still be used, just need a small perf PCB for the input XLR section.
Most of the other changes on the new PCB revision 2 are minor... i.e. shifting parts a few millimeters here and there, adding extra pads for test points, or "future use", moving the mounting hole backwards, adding new mounting holes for additional support in the back, shifting locations for 1 molex connector, etc. minor stuff.
Have you settled on a definite set of uses for the 6 switches/positions?
VU Meter on/off
CH1 phantom power
CH1 polarity reverse
CH2 polarity reverse
CH2 phantom power
Main power switch
-
VU Meter on/off
CH1 phantom power
CH1 polarity reverse
CH2 polarity reverse
CH2 phantom power
Main power switch
Cool. The polarity switch certainly won't hurt anything, but probably won't be used much in the field (which probably has been mentioned). Personally, I'd probably rather have the polarity jumpered/fixed inside the case. This would eliminate two toggle switches and two holes on the front plate, and not require reworking the PCB (of course it's another option you could offer, but I'd just ditch it for the TS-2). Or some other feature could replace the polarity control's front panel real estate with few complaints I bet ;D
SO, here goes Sanaka's cartoonish Photoshopped mockup of the TS-2 front panel, which may or may not be helpful in any way :):
(http://sanaka.smugmug.com/photos/349488747_LwmRu-L.jpg)
Also, there was some discussion of the power connector and how it would be nice if it were right angle and locking. Again, don't know if this is any help, but these connectors (http://www.mcmaster.com/ctlg/DisplCtlgPage.aspx?ReqTyp=CATALOG&CtlgPgNbr=747&RelatedCtlgPgs=746,747,748,749,750,751,752,753,754&WRQuickLinks=Electrical%20Connectors&sesnextrep=424026103138972&ScreenWidth=1600&ToolsetID=ToolPageFlip&ToolsetAct=) at McMaster Carr (http://www.mcmaster.com/)look pretty solid, though pricey. Particularly, part# 6897K83 looks like a great panel connector, if one wanted to interface the matching RA plug to their power source (images show 4 pole and 3 pole versions, whereas 2 pole is good for just 12V DC to the preamp).
(http://www.mcmaster.com/catalog/114/gfx/large/6897kp6l.gif)(http://www.mcmaster.com/catalog/114/gfx/large/6897kp5l.gif)
G'Night!
Peace,
Sanaka
-
ha! i order from mcmaster all teh time, and have never once though of using them as an electronics supplier!
-
I second Sanaka's feelings on the polarity switch. Never used one, would be better if it were a -20 pad for line in from a hot SBD patch.
-
ha! i order from mcmaster all teh time, and have never once though of using them as an electronics supplier!
Yup. They even have Greyhill rotary switches! Here's a fun power connnector I just from them. a 50 Amp plug. Like 5" long, like $83.
Peace,
Sanaka
-
I assume so because you've emphasized that you usually go through several board revisions before releasing a project officially, but I didn't see where you mentioned it specifically regarding this problem.
Well, I thought more about it and after getting some sleep my mind is clearer.
The current PCBs can still be used without any problem for "stock version" preamps... (no input transformer installed) without any modifications.
The new PCB revision 1.2 will be more suitable for preamps with the input transformer option installed.
-
I second Sanaka's feelings on the polarity switch. Never used one, would be better if it were a -20 pad for line in from a hot SBD patch.
Or a high pass filter (80 Hz cutoff)? :)
-
I second Sanaka's feelings on the polarity switch. Never used one, would be better if it were a -20 pad for line in from a hot SBD patch.
Or a high pass filter (80 Hz cutoff)? :)
or that too. how useful is a polarity switch in the field?
-
how useful is a polarity switch in the field?
For tapers taping a concert? Probably not useful.
For the home studio user close miking instruments/drums/etc... useful.
I hope tapers won't be the sole users of this preamp.
Trying to cast a bigger net, so prices can be lowered. Big market = lower price, small market = higher price
If tapers really want filters... hmmmm... Here's the thing... my design is not a dead end. I've got plenty of real estate space on the switchboard. And the switchboard can even be made bigger by 3" deep. Plenty of room to accomodate future features. Heck, I can design a new switchboard with a totally different set of features, more stuff and use it with the existing motherboard pre... the future looks bright.
Don't forget... we have a modular design here... the motherboard containing the actual preamp + PSU and a daughterboard containing the switches, PP softstart and the PP PSU. ;)
-
I would rather have a HP switch ~80-100 Hz
than a polarity switch
but I'd be doing mostly field recording with it
-
Man, where were all you guys when I was asking around for suggestions? :)
The people who don't want/need HP filters presented good arguments and convinced me... i.e. don't throw away anything, if filtering needs to be done, we do it in post... you'd have more control over cutoff frequency, Q factor, amount of attenuation, dB/octave, etc...
The techie in me sees that without filtering, it's less opamps required, which means less power consumption, which means longer battery life.
...
Alright, for the pro-filtering crowd, present your arguments, if I'm convinced, I may make a separate switchboard version with HP filtering.
-
Man, where were all you guys when I was asking around for suggestions? :)
The people who don't want/need HP filters presented good arguments and convinced me... ... if I'm convinced, I may make a separate switchboard version with HP filtering.
I was right here :)
http://taperssection.com/index.php/topic,105112.msg1413766.html#msg1413766
BTW: The reason I like the high-pass on the preamp is that it's not always convenient to access the same on the mics (blimps, on stands, out of reach etc) or the mic/s may not have that feature.
I do a fair amount of studio work BTW (usually close miced solo instruments) and as a consequence, never need phase inversion. But I understand that YMMV and the feature broadens the appeal :)
The features I have actually used on my MixPre for field-recording are ...
1. P48.
2. HP Filter.
3. Mono --> Stereo mix (ability to send one input channel to both or either outputs the - L,C,R switch). Great for when I mess up the stereo connections (which is often ;D ), possibly as I know I can fix it on the pre I have become lazy.
While I like the limiter in it, it rarely has to kick in, so is not necessary.
digifish
-
a hp filter is pr0lly of more use for location recording than music recording
it helps to prevent low freq wind noise from clipping the preamp
tip: aside from live and studio music recording there is a whole 'nother market of film/video, sound artists and nature recordists/bio-acousticians who are waiting for a serious, pro-quality, affordable, low noise/high gain preamp
:)
-
it helps to prevent low freq wind noise from clipping the preamp
Hmmm.... that's a good argument.... the low freq rumble may clip the pre/AD/etc...
there is a whole 'nother market of film/video, sound artists and nature recordists/bio-acousticians who are waiting for a serious, pro-quality, affordable, low noise/high gain preamp
Thanks for the tip. What kind of mics do they typically use? Dynamics or Condensers? I'm assuming leaning more towards condensers?
-
it helps to prevent low freq wind noise from clipping the preamp
Hmmm.... that's a good argument.... the low freq rumble may clip the pre/AD/etc...
there is a whole 'nother market of film/video, sound artists and nature recordists/bio-acousticians who are waiting for a serious, pro-quality, affordable, low noise/high gain preamp
Thanks for the tip. What kind of mics do they typically use? Dynamics or Condensers? I'm assuming leaning more towards condensers?
Nearly all condensers.
digifish
-
Man, where were all you guys when I was asking around for suggestions? :)
Ditto, I was right here as well and put my two cents in on that a couple times. :)
Truthfully, I've been a bit bummed since I double-checked a little while back for your feature set and found that the HPF wasn't included -- went from pretty excited about this preamp to just a sideline observer. I know from a design standpoint you've got to make choices and there are tradeoffs, but I'm not sure I personally can get used to having a preamp without a HPF.
Figured I'd just let it lie, but if you want arguments:
I know nothing about home studio users, but I'd imagine most do a significant amount of post-processing, editing, mixing, etc. The same argument about doing it in post as is applied to the HPF need seems to work here -- if studio users need to reverse phase on a channel, it can be done easy enough in post.
As to HPF, everyone says do it in post or else risk losing the low end without recourse. I don't get that, esp when many people on ts.com will say with 24bit recorders you can record with alot of headroom, say record at -12dbFS, and then normalize in post. If you do this, you will raise the noise floor by 12db when you normalize. Probably not a big deal given the dynamic range of a 24bit recorder, but it's the same thing that would happen if you want to reverse the HPF you applied in the field.
Here's the scenario as I see it: Apply HPF in the field when you think you need it, say 80 Hz/6db slope. So you will be filtering at -3db attenuation at 80Hz (the filter knee), sloping to -9db attenuation at 40Hz, and -15db at 20Hz. You get home and decide you were wrong -- the low end is not gone and lost as everyone always says, it is just attenuated. So you design a reverse filter to raise the 20Hz range by 15db, rising to 9db gain for 40Hz, and 3db gain for 80Hz. You've just reversed your mistaken application of the HPF, with the penalty that the noise will be raised by 15db at 20Hz, 9db at 40Hz, and 3db at 80Hz. Really probably not much worse than normalizing a 24bit recording that was purposely recorded at -12dbFS and then normalized to 0dbFS.
Flip side is that if you really needed the HPF. In this case, if you used it in the field, you're golden and you've maximized your signal to noise ratio (say for example recording perfectly so you are just short of 0dbFS). If instead you record without a filter and decide to apply the HPF in post, you will apply the HPF with software at home and will then attenuate those low frequencies. Since low frequencies hold a lot of energy, once you apply the HPF in post, you will reduce the overall volume of your recording, say now post-filter it is at -3dbFS. Ok, then it's time to normalize and you raise the gain by 3db -- and in the process raise the noise floor of your recording by 3db compared to what you could have done in the field had you applied the HPF then.
Bottom line, whether you do HPF in the field or do HPF in post, if you prefer a certain amount of low frequency content to your recording there will be a risk either way. If you do HPFiltering in the field and need it, your recording will have a better signal-to-noise ratio across the spectrum compared to a recording made without HPF, with the filter applied in post and then the recording normalized to 0dbFS. Or you apply HPF in the field, find you don't need it and need to reverse that filtering by adding gain to the low frequencies in post -- and again raising the noise floor. Since I have a good idea when I need HPF and when I don't, I'd rather apply it in the field and try to get the best recording I can. If I'm wrong, I'll fix the mistake in post and take the hit on a higher noise floor, but I know I'll be right much more often than I'm wrong.
Getting back to the design of the preamp, I think that is pretty much always the case -- provide full functionality, or decide to have limitations in your hardware that will need to be addressed with post processing. HPF can be skipped on the pre, requiring users to fix that in post, or phase reversal can be skipped, requiring those users to fix it in post. For that matter, you could easily skip the 10db trim pots and just have 10db (or 6db) stepped gain. Users who want to fine tune gain can do it in post with software rather than applying it in the field.
Really none of these choices should be a deal breaker -- there have been plenty of fine tapes made by the no-frills m148 (with just a straight 20db gain and no other features), even going into a Benchmark 2496 which also has somewhat limited options for gain -- but different potential users will have different perceived needs as to what is absolutely vital.
Ramble, ramble......anyway, good to know HPF might come along in a future version. :)
-
FWIW and since you solicited for opinions, I'd also use HPF and wouldn't use polarity switches in the field. I know that you are trying to make this a universally applicable product, but after all it does seem as if you've targeted this market with the product, maybe even with the naming of the preamp. I'm not trying to imply there's any obligation of course to suit the needs of any particular market, but since you're soliciting opinions here, it's already been probably concluded correctly that more field/location recordists would want HPF than polarity switching.
Another thing as a FWIW, is that this feature I think could help differentiate your product, if it needs differentiating. Most smaller preamps in the 'affordable' end of the price range that I know of don't have any filtering. Many of the higher end products do. Course, that could also be said of the polarity switching feature too, so maybe that point is a wash.
However, having said this, in the end, ensuring you have a small pre-amp that provides a great sound/low noise combination at an affordable cost will probably be the biggest differentiator. My opinion.
-
Thanks tonedeaf, Todd, and others. Your arguments and explanations have shone the light on me :)
Here's where I'm at.... Since I only ordered 10 prototype board sets of the Revision 1 PCB, and now I'm in the process of doing a Revision 1.2 (to fix the PP problem and other little irritations),... I think I'm going to HOLD OFF sending out Rev1.2 to the factory.
And instead redesign the Motherboard and Switchboard to include HP Filtering. ;D
Nothing to feel bad about. These 10 boards are not a total loss for me, they can still be used without the input transformer option for other users (tapers or studio recordists). ... and hopefully I can recover my cost for these 10 boards.
So here's what I'm thinking... The new set of (6) switches will be:
VU Meter ON/OFF
Phantom CH1
High Pass Filtering (both channels)
-20dB Pad (both channels)
Phantom CH2
Power ON/OFF
So that low level signals wouldn't travel up and down between the motherboard and switchboard PCB, I'm going to use mini-sealed Low-Signal Relays on the motherboard. Only the control signal will be coming down from the switchboard to the motherboard, to enable/disable the switching relay. Also... using a single switch can control both channels simultaneously via relays.
Just a headsup... power consumption will go up due to additional opamps and relays (when engaged).
HP Filtering.... Please vote!
60Hz
80Hz
120Hz
Also how much attenuation?
a shallow 6dB/octave,
12dB/octave,
or steep 18dB/octave?
I'll have to breadboard and play with some filters.
Project delayed.... until we have some HP filters working :) :)
-
So here's what I'm thinking... The new set of (6) switches will be:
VU Meter ON/OFF
Phantom CH1
High Pass Filtering (both channels)
-20dB Pad (both channels)
Phantom CH2
Power ON/OFF
You have my ideal choice with those six. The one thing I have never had use for though is I have never run phantom on just one channel. So if you tied phantom to both channels you would have room for another option on switch 6.
Just a headsup... power consumption will go up due to additional opamps and relays (when engaged).
we're a resourceful lot, remote power can be found
HP Filtering.... Please vote!
60Hz
80Hz
120Hz
Also how much attenuation?
a shallow 6dB/octave,
12dB/octave,
or steep 18dB/octave?
my vote is for 80Hz, 6db/octave
-
So here's what I'm thinking... The new set of (6) switches will be:
VU Meter ON/OFF
Phantom CH1
High Pass Filtering (both channels)
-20dB Pad (both channels)
Phantom CH2
Power ON/OFF
So that low level signals wouldn't travel up and down between the motherboard and switchboard PCB, I'm going to use mini-sealed Low-Signal Relays on the motherboard. Only the control signal will be coming down from the switchboard to the motherboard, to enable/disable the switching relay. Also... using a single switch can control both channels simultaneously via relays.
Just a headsup... power consumption will go up due to additional opamps and relays (when engaged).
HP Filtering.... Please vote!
60Hz
80Hz
120Hz
Also how much attenuation?
a shallow 6dB/octave,
12dB/octave,
or steep 18dB/octave?
Project delayed.... until we have some HP filters working :) :)
Great to see this feature make it back in. I vote:
80 Hz 6 dB / Octave
OR
60 Hz @ 12 dB / Octave
(if it's for wind & rumble reduction, this is about right & conservative)
FWIW: Sound Devices uses
MixPre: (http://www.sounddevices.com/products/mx2master.htm) 80/160 Hz @ 6 dB / Octave (I have found this slope to be a little underdone @ 80 Hz that I use, if anything, but that's better than over-doing it)
302: (http://www.sounddevices.com/products/302master.htm) 80/160 Hz @ 12 dB / Octave
while the 442 (http://www.sounddevices.com/products/442master.htm) is sweepable 80 Hz to 240 Hz, 12 dB/oct at 80 Hz, 6 dB/octave at 240 Hz
...just to confuse us all :)
digifish
-
EDIT: MAN, I'm a slow typist. Please excuse the now redundant portions of the following post ::)
+T to ToddR:
Since I have a good idea when I need HPF and when I don't, I'd rather apply it in the field and try to get the best recording I can. If I'm wrong, I'll fix the mistake in post and take the hit on a higher noise floor, but I know I'll be right much more often than I'm wrong.
Besides wind rumble outdoors, sound pressure is so much greater at bass frequencies that sometimes the bass can overwhelm the main range of program material, especially indoors due to 'cabin gain'. My own experience w/ this is recording an acoustic gig inside, in a small space, and everything's fine except one drum (especially a Djembe) just flailing the inputs. If I simply adjust gain for good levels, the capture ends up just all drum with the main range of the material too soft. Like TodddR describes ;D So a simple low-cut EQ is, well, yah, like peeps are saying :) I also let the issue lie when it came up before because it seemed like maybe a feature bloat thing in this case, plus you mentioned it might involve sending low mic level signals between boards, a very good thing to avoid. If you can integrate it as well as you're bringing everything else off so far, I'd think it can only help sell units.
One idea in this regard: could the low-cut (I always think of it as low-cut, but HPF or whatever) be done on a daughterboard that could socket on to the main board later? That way your test and revision process wouldn't have to delay development/release of the TS-2 as is. Folks could get it and use it with the knowledge they can add an awesome low-cut later.
OR, you could draw the line at some point and tell everyone here to go fly their respective kites and take your product as you make it :P I don't think the Aerco has a low-cut, yet remains highly respected, for instance.
Peace,
Sanaka
-
The one thing I have never had use for though is I have never run phantom on just one channel. So if you tied phantom to both channels you would have room for another option on switch 6.
This is of course true, probably more convenient 99% of the time, and if there is another feature to put in slot 6 (sheesh...let's think about cutting 5Fish a break!), then by all means. However, I can think of one reason to leave L/R phantom separate: for someone doing an interview and using two separate and different mics. Like a cardioid for close speech plus an omni for ambience. Granted, not a big market niche, but if it's easier to leave the design with separate switches and there's no real potential for another thing at slot 6, then why not suit that tiny niche too.
For the filter I vote 80hz X 12dB. Still not terribly aggresive, and like ToddR was saying, bringing up just bass in post doesn't hit the S/N as bad as having to boost everything but bass.
Peace,
Sanaka
-
Here's a revised image, just because I get off on doing this. Sorry to be all post happy.
(http://sanaka.smugmug.com/photos/350247623_FidV3-L.jpg)
Peace,
Sanaka
-
Just a thought...and this isn't a vote by any means...I'm just throwing this out there...
I once had a battery box from Sound Pros that was rather inexpensive (I think $80 for the whole thing and $50 w/o the roll-off feature???) that had a pair of dip switch panels, one per channel. Each panel had I think 4 switches. The dip switch panels are very small...maybe 1/2 to 3/4 inch long and you need a pencil tip to switch the position of each individual dip switch. On the back side of the battery box, there was a permanently affixed chart that showed which position each of the switches needed to be in for a certain roll-off frequency to be in effect.
I know that every little mod adds cost, but is there an inexpensive way to incorporate dip swiches into the design so that a range of roll-off frequencies and attenuation levels could be user selectable? The front cover switch might engage the roll-off feature, but the dip switches would determine the frequency and attenuation level.
If yes, then I'd suggest that the switches reside inside the box cover, or maybe underneath a separate access cover, because honestly once I set mine initially, I didn't change it much after that AND the switches can get bumped accidently on the outside. OTOH, this was frequency variable only...so if there was also option for attenulation level, I probably would have changed the switch position more often. Anyways, it definitely was a nice feature and having these as a varioable option would be a unique feature that even top end pre-amps (to my knowledge) don't have.
Like I said above, I'm not necessarily suggesting this, especially if there _IS_ a concensus of what the best frequency and atten level is, since every additional component adds more cost.
-
I don't think the Aerco has a low-cut, yet remains highly respected, for instance.
Highly respected among used-market buyers. If you have to buy it direct, you lose a significant amount of respect for the product before it finally arrives. Sorry, just telling it like it is. That is one reason I'm so keenly interested in this product, so I can sell my new Aerco and hopefully have something with greater functionality and similar size/performance. BTW, correct the Aerco has no low cut.
FWIW, if you end up taking 5 or 6 months to deliver a pre-amp chances are good your product could lose alot of respect too unless you tell people ahead of time that's how long it will take.
-
OK, Sanaka...you got post happy...now it's my turn. :)
Since you're now talking about going back for another board design, is the overall size of the unit a given? I know that you have a case selected, so I suspect that the answer is 'yes' that the size has already been fixed.
However, the reason I am mentioning this at this late stage of the game is that, as you said, a new board is in the offing, and I didn't see a whole lots of discussion early on about size optimization. For example, you'd mentioned that there was some extra space in the final design that you could use for potential add-on features or customization.
FWIW, in a perfect world (and forgive me again because I do realize that you're probably past this point) I'd vote optimizing the inside space to save an inch or two on the depth over keeping the extra space. But again, I know this hasn't been a subject that has been put up for discussion, so please just ignore it if it's unreasonable to consider at this point.
-
Thanks all for the responses!
Here's a revised image, just because I get off on doing this. Sorry to be all post happy.
Looking good.
The dip switch panels are very small...maybe 1/2 to 3/4 inch long and you need a pencil tip to switch the position of each individual dip switch.
The dip switches are cheap and along the parts around it. What makes this feature expensive is the machining of the case openings. Don't forget, I'm not a big manufacturer with deep pockets for custom case building :) I wish!
Dip switches. Good idea. I'll put this in the back of my mind...
If you have to buy it direct, you lose a significant amount of respect for the product before it finally arrives. Sorry, just telling it like it is.
I don't know the Aerco so I'm not sure what you mean by losing respect.
FWIW, if you end up taking 5 or 6 months to deliver a pre-amp chances are good your product could lose alot of respect too unless you tell people ahead of time that's how long it will take.
I'm not sure what that respect is all about, but I think bringing a schematic plan to a functioning preamp in 3 weeks in front of all your eyes is something good :)
And I hope it doesn't take me 6 months too... need some income soon to recover all these R&D costs. But I also don't want to promise that on a certain mm/dd/yyyy date, it's available for sale. One thing I can guarantee is I'm doing this as fast as I can, and still keeping an eye on quality.
I want /hope/wish to shoot for Thanksgiving or before Christmas. January is a bad time to release a product as everybody gets credit card bill shock.
Since you're now talking about going back for another board design, is the overall size of the unit a given? I know that you have a case selected, so I suspect that the answer is 'yes' that the size has already been fixed.
Yes, I've already selected the case so the PC board size has it's minimum width limit and maximum length limit.
If maybe thousands of customers order the first gen preamps, I'd become a big company and then I'll be able to do custom cases and make a next gen preamp that is smaller :)
Ahhh, exactly how much drain do the VU meters put on the total draw? If I wasn't given the option of turning them off it wouldn't bother me. That's another switch to keep your reverse phase in the mix. I see a use for that if you were running a second rig capturing audience/room from stage with mics facing said audience. Granted, this is done more with multi track recording but something like this could pop up.
Now, that we're adding relays and opamps, maybe conserving power by adding an ON/OFF for the VU meter is a moot point.
Any EASY suggestions for the 1st switch? :)
-
i think what tonedeaf was reffing to is turn around time. after this is on the market and you are taking orders. if i pay on 08/12 i should receive the product before xmas. as far as switches go, i like the meter switch b/c some may need the lights off to not attract unneeded attention.
-
As far as the dip switch idea, I was dreaming. However, I think the concept of having the dip switches inside the case for user defined settings (you set them to preference and then leave the case closed until you want to change them) has merit if you think that special machining of the case is too expensive to bother about.
Just to clarify my earlier message about the Aerco...I guess I shouldn't beat around the bush. Jerry Chamkis is one of the nicest guys in the world, but I sent him $750 for a preamp on Jan 1 of this year. He told me at that time that his delivery schedule was about two months. Around a little after 2 months after sending the $$ and not hearing from him, I started asking. That started a loooong string of communications in which I received promises about when I'd get the product and then I didn't receive anything. Finally, at least 6 to 8 promises later, I got my product at about 4 1/2 to 5 months. He admitted many times to me that his priorities are with other projects, so when his priorities change back to preamp manufacture, I'm sure this situation will resolve itself.
So, my previous comment was basically just saying that while I and everyone else I'm sure understands that you're a one-man show, delivery in less time and service with a little more reliability are something that will help you to beat one of your competitors.
-
I see... well a lot of you guys are real nice and have PM'd me about placing a pre-order to help with funds during this stage and I said "Thanks but No, just wait until it's ready."
(1) It's not my style to take pre-orders at this early in the game. I won't take anyone's money if I don't have a ready product to deliver.
(2) Only time I take pre-orders is if there is already a product and is just OUT OF STOCK, and I'm just waiting on some suppliers to deliver missing parts then I can start shipping again.
(3) The whole pre-order is unfair to the buyer. You lose your money, I get to keep it and you have nothing to show for it.
(4) Paypal has rules that I must deliver the product within X amount of time. Pre-orders and group buys (where the product is not yet available) is not allowed.
If there is a dispute and Paypal asks me "John Doe paid you $9.99 on the 1st, where is his product? I want to be able to reply with here's the tracking #, shipped out on the 4th"
Even right now, I have people wanting to place orders for my new PSU kit (for racking console preamp modules).
(http://farm4.static.flickr.com/3201/2756319605_e05b21b697.jpg)
The product is ready, I have the parts but I just haven't had the time to pack them. I told them... wait until later this week, or next. It will be ready to ship out by then.
having the dip switches inside the case for user defined settings
That's the plan... but will depend if there is space available. I'd be adding relays and other stuff, and right now it's already jam packed as it is.
My current CAD license limits me on how big a PCB I can create. If I want to create bigger boards, I'd have to upgrade to the next level. At this point, it's a $600 upgrade.
I think I'd have to bite the bullet on that one. If I do upgrade, I can extend the depth and use PCB mounted XLR jacks and more switches in the rear (maybe recessed slide switches for other functions... like polarity reverse without using relays)...Hmmmm...
-
Any EASY suggestions for the 1st switch? :)
Sure! Any time I hit that switch, the guy that's next to me at a show that's either clapping or talking or singing out loud automatically stops!!! How much would that cost to add? ;D ;D ;D
...adding a couple of compoents to the preamp design...$10.
...a finished preamp with everything that TS.com ever wanted on a premap $500 (or whatever)
...being able to make assholes disappear with the flick of a switch...PRICELESS!!!!
-
"Sure! Any time I hit that switch, the guy that's next to me at a show that's either clapping or talking or singing out loud automatically stops!!! How much would that cost to add? Grin Grin Grin"
Hmmm, I'd pay extra for that option, maybe something taser-like? <grin>
-
it helps to prevent low freq wind noise from clipping the preamp
Hmmm.... that's a good argument.... the low freq rumble may clip the pre/AD/etc...
this is a big problem for people who work outdoors
it is usually solved with shaggy dogs (or 'dead cats' as they're referred to on TS) and zeppelins
but a hp ~80 - 120 helps keep low freq info out of the recording
this could also be low freq coming thru a stand/tripod caused by any sort of mechanical vibrations
there is a whole 'nother market of film/video, sound artists and nature recordists/bio-acousticians who are waiting for a serious, pro-quality, affordable, low noise/high gain preamp
Thanks for the tip. What kind of mics do they typically use? Dynamics or Condensers? I'm assuming leaning more towards condensers?
never dynamics - always condensers
popular single mics are the AT3032's, Røde NT1A's and the MKH series
single point mics are AT822 and NT4
but most people use whatever they can afford
-
w/r/t DIP switches for hp:
I've used a SP preamp for a few years now
my pre has the DIP switch for selecting the hp cutoff freq
I have never really like this arrangement
because in the field things tend to get 'fumbly' real fast
to change or turn on the hp you have to:
- turn the unit over to read the chart telling you which DIP switches to switch for a particular freq
- find something to switch them with - fingers vary in size and dexterity
then repeat this process when needing to turn them off again
I have often wished for a simple easy switch I could throw for a 80Hz hp
instead of fumbling with a set of DIP switches when trying to capture a great sound out in the field
my 0.02
added:
also over on the micbuilders list there was some concern about there being mV of oscillation in your preamp design?
not sure what the poster was referring to here but where is the oscillation exactly? on the rails? output?
-
80Hz seems to be the magic number popping up often.
What's the dB/octave? 6, 12, 18?
Is a steep or shallow rolloff preferable?
I'm leaning towards 6dB/oct so we don't kill too much of the low end.
How about a compromise... 100Hz (in between 80 and 120Hz) at 6dB/oct?
-
w/r/t DIP switches for hp:
I've used a SP preamp for a few years now
my pre has the DIP switch for selecting the hp cutoff freq
I have never really like this arrangement
because in the field things tend to get 'fumbly' real fast
to change or turn on the hp you have to:
- turn the unit over to read the chart telling you which DIP switches to switch for a particular freq
- find something to switch them with - fingers vary in size and dexterity
then repeat this process when needing to turn them off again
I have often wished for a simple easy switch I could throw for a 80Hz hp
instead of fumbling with a set of DIP switches when trying to capture a great sound out in the field
my 0.02
The basic concept I presented is that the front swich on the face activates the low cut. Therefore, no field fumbling...only on and off. The dip switches would be on the inside of the box so they couldn't be bumped around. You'd pre-set the dip switches based on your personal preference by opening the box and setting them yourself. But this would allow for user selectable settings for both frequency and level cut. In the end though, it's up to 5fish to decide if the design has space or merit.
-
80Hz seems to be the magic number popping up often.
What's the dB/octave? 6, 12, 18?
Is a steep or shallow rolloff preferable?
If you end up going with a single setting, my vote would be just a scosh higher than 80hz...and 12db.
Reason I chose 12db is most low cut users I would think would want it for balls-out shows where there's simply no subtleness to the low end. In that case, I'd rather that the low cut has some nuts to it to really beat down the bass...instead of a wimpy-ness to it which is more fixable in post. IOW, err on the side of taking out too much bass with the cut rahter than not enough. My thoughts...
BTW, I'm soft on this though and I'd go with the majority opinion for sure, especially if someone feels strongly.
-
Reason I chose 12db is most low cut users I would think would want it for balls-out shows where there's simply no subtleness to the low end. In that case, I'd rather that the low cut has some nuts to it to really beat down the bass...instead of a wimpy-ness to it which is more fixable in post. IOW, err on the side of taking out too much bass with the cut rahter than not enough.
Ditto for me exactly. 12dB slope right around 80 or a little higher. Seems some folks are routinely recording kinda low and boosting their whole captured signal by 12dB in post. I tend to try for a hotter capture, and would much rather bump up only the bass in post if the low cut turned out to be a little more than was needed.
Peace,
Sanaka
-
any comment on this?
also over on the micbuilders list there was some concern about there being mV of oscillation in your preamp design?
not sure what the poster was referring to here but where is the oscillation exactly? on the rails? output?
-
any comment on this?
also over on the micbuilders list there was some concern about there being mV of oscillation in your preamp design?
not sure what the poster was referring to here but where is the oscillation exactly? on the rails? output?
Not sure on what basis anybody has made this statement. If you take the time to look through this thread, you'll read about the issues that have been encountered and what has been done to resolve them. I don't recall reading anything about what you're talking about.
Regarding outsiders commenting on the design and whether there are issues, it's not like anybody has his preamp in their hands to test it themselves to independently determine if there are issues, but honestly, to me that's not all that relevant because 5fish has gone above and beyond in terms of full disclosure in this design and the issues that he's encountered.
So, if they're talking about the concern over microphonic sounds that he discussed a page or two back, that has been resolved as his posts have stated. If you're talking about signal stability, waaay back a ways he shows some old-silly-scope images that are dead flat.
-
sorry I meant for that post to be directed to fivefish
but someone on the micbuilders list had mentioned reading on fivefishes blog something about there being a few mV of oscillation
but the post wasn't specific about where the osc was occurring or what fivefishes plan was to deal with it
so, I am curious in fivefishes response to this statement
-
reading on fivefishes blog something about there being a few mV of oscillation
Here's my blog and go read ahead. FYI... this is like May of 2007, the SC-1 pre was just an idea on it's first prototype.
http://www.fivefish.net/diy/sc1/
This is the development blog of my SC1.
(http://www.fivefish.net/diy/sc1/images/sc1-test1.jpg)
Photo of first prototype.
As bad as this prototype looks, it can already do 100Khz!
(http://www.fivefish.net/diy/sc1/images/sc1-100khzpreout.jpg)
On testing the VERY FIRST PROTOTYPE.. I had a part there where I mentioned .
Noticed some slight oscillation at the 5th, 6th, and 7th gain settings of the selector switch. So finally fixed that with additional bypass capacitors on the supply rails. We're talking about less than 0.2Volts oscillation on top of a 30Vpp output. So it's insignificant. But still, it's gone now. :)
As I said, this is Rev1.00 PCB I'm working on and it looks like on my Rev3.00 PCB, I've already incorporated those caps in the design.
Then connected the mic pre circuit output to the balanced line driver. And what do you know... the less than 0.2Volt oscillation fixed itself. The addtl caps weren't needed.
And then a few days later, I posted
VU meter readings are better... especially at the 11th and 12th position. Oscillation at the higher gain settings fixed too.
I am curious in fivefishes response to this statement
My comment.... if they're gonna comment about some oscillations I mentioned, man! READ THE ENTIRE STUPID BLOG and preferably have some READING COMPREHENSION. i.e. don't just pick and choose what I said one day and ignore what I posted later on... pick also the part where I said the problem was fixed during the later days. If you have ADHD, don't read my development blog. Just read the last page where everything is fixed, and ready for sale.
The whole blog is my daily diary of what's happening in the course of development and prototyping.
-
mr. fivefish, please lock this thread and start a new one. its under additional options>modify 1st post>lock (i think). then, link to the last thread in the 1st post of the second thread. this happens to every thread at 25 pages. :)
this thread has been fantastic nerding out material. +t
-
Will do... thanks!
Continuation of thread can be found here...
http://taperssection.com/index.php/topic,108569.0.html