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Author Topic: New TS-2 Preamp ... under development (part II)  (Read 49609 times)

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Offline fivefishdiy

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Re: New TS-2 Preamp ... under development (part II)
« Reply #30 on: August 13, 2008, 05:32:06 PM »
Ch-Check it out!  We're going places.  ;D

My SC-1 preamp has been mentioned again in MIX Magazine. Wohoo!

Note: The TS-2 preamp is based upon my SC-1 preamp design.... just a different form factor (stereo) and options for input transformers.

AUGUST 2008 issue

Field Test: Avant Electronics Avantone CK-40 Stereo Mic
http://mixonline.com/gear/reviews/audio_avant_electronics_avantone/

and also back in MAY 2008 issue

Field Test: Peluso 22 47SE Tube Microphone
http://mixonline.com/gear/reviews/audio_peluso_se_tube/


BTW, check out the review of the CK-40 stereo mic. This could be a good mic for tapers.





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Offline fivefishdiy

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Re: New TS-2 Preamp ... under development (part II)
« Reply #31 on: August 13, 2008, 06:27:38 PM »
Well, it would behoove you to look into that mystery.  Not trying to bust your balls here, but if somebody asks you about battery life with some battery they are using--let's say, for grins, a lantern battery--you ought to know the current draw at that voltage.  Right now, your answer is 104mA, which is about 0.6W.  But if they use a 12V battery, it's 115mA, for 1.4W?  Does not make sense.

BTW, the earlier tests do not have the 48V converter running. i.e. switchboard not connected yet.

Okay, I've been working on this mystery this afternoon. I decided to repeat the test using a Bench Power Supply. So if the Tek battery has some weirdness to it due to it's built in converter, I'd remove that equation from the test. So here I am using a linear HP regulated PSU, plugged into the wall. 

Set it to 12.01 VDC output.
Feed the voltage to the DC jack of the preamp. Get my 'expensive' Fluke and inserted it in between, to measure the current before going into the preamp.

With both PP switches off, I get a reading of 125.7 mA
Turning on one of the PP switch, without any mic connected, I get a reading of 130mA
Turning on both the PP switch, without any mics connected, I get a reading of 133.9mA

Loaded one channel with my power hungry mic... both channels PP ON, I get a reading of 143.8mA

Okay, still with me so far?..... The theory is if we lower the voltage, current consumption should go up. Right?

Without changing the preamp/mic/phantom power setup, I slowly turn the dial on my HP regulated PSU down to 6.0 Volts...

12Volts = 144mA
10Volts = 145mA
09Volts = 147mA
08Volts = 150mA
07Volts = 147mA
06Volts = 137mA

Current did go up as voltage went down to 8Volts... then from 8Volts down to 6Volts, the current consumption got reduced. 

In all voltage settings, the mic pre and the attached mic was still working.

If not, you have a massive loss in your converter circuit at higher supply voltages.  I doubt that is the case, because that would be one hot puppy.  But it's worth nailing down.

There's probably some efficiency loss. I'm not claiming close to 100% efficiency, or even above 90+% efficiency. But right now, the converters run cool to the touch and have no problem powering the preamp.

I've been monitoring closely if either the split or the 48V converters get hot since day 1. But they don't even get warm. Defnitely, not hot. And I've been running this on and off for several hours straight.


Thanks for your inputs! Much appreciated!  I'll tackle the PP one of these days.





 


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Offline it-goes-to-eleven

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Re: New TS-2 Preamp ... under development (part II)
« Reply #32 on: August 13, 2008, 06:53:37 PM »
Metering lights or, in my case, running lights... help me know that my system is running.  If I switch the lights off and then get side tracked, I may very well come back and think that A) I've run out of juice, or 2) someone switched off  the pre. 

You could always try touching your tongue to the battery.

Note: Your max dBu output will be reduced when running on reduced voltage input than 12V. i.e. lower headroom. But then again, you probably don't need +23dBu output whipping the inputs of your AD converter.

Curious what that might mean in terms of headroom when run on 9volts.

Fwiw, I really like the sony camcorder batteries that power the 7xx recorders. Especially the way they attach to the recorder to make a solid unit with no cable worries.   I rarely removed the battery from the 7xx and preferred to just plug the whole unit into the charger.  At 8 initial volts and droping to 6.5-7.0, I know that is a bit low for your design..



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Offline Ben Turnbull

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Re: New TS-2 Preamp ... under development (part II)
« Reply #33 on: August 13, 2008, 08:31:54 PM »
Metering lights or, in my case, running lights... help me know that my system is running.  If I switch the lights off and then get side tracked, I may very well come back and think that A) I've run out of juice, or 2) someone switched off  the pre. 

You could always try touching your tongue to the battery.

<snip>


 ;D

Hey, this is going to be a can of worms but I've got to ask... I've seen boxes with Mid/Side on the fly reduction features.  What's involved with that and is it a one switch/on-off deal or is there a pot or something else working as well?  I want to run M/S some times but have not due to the hassle that I'd have in post.

I'd also like a pair of RCA line outs as well... in fact, apart from the lock ability of an XLR jack, is there a reason unbalanced outs wouldn't be enough on their own?   'Just trying to learn here by asking the amateur questions.  :)


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Offline fivefishdiy

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Re: New TS-2 Preamp ... under development (part II)
« Reply #34 on: August 13, 2008, 09:04:55 PM »
Well now that's getting a little interesting.  Is the DC converter output not at a fixed voltage?  If it's dependent on voltage input fluctuations, I guess that explains the loss in headroom.  I believe the chip you're using for 48V doesn't work that way though; it uses a fixed reference for output voltage.

Open question whether it's better to operate at a fixed internal voltage and draw more current from the power source as a result.

The split psu is a fixed voltage output.  The 48V converter has a fixed reference voltage. On the 48V section, I just use a trimmer to fine-trim the output voltage.

Anyways... I am keeping a close eye on the split psu converters because when I add that high-pass filter section, plus the pad switching (so that will be 2 opamp chips and 4 relays total for the 2 channels), I'll be cutting it close to the max. wattage rating of the converter. 

I compute I'll still come under it, but we'll see. Otherwise, I may need to devise a different solution.


Man... what's the power consumption of the other preamps you guys use?


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Offline fivefishdiy

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Re: New TS-2 Preamp ... under development (part II)
« Reply #35 on: August 13, 2008, 09:08:47 PM »
MS feature I'm not even considering.

a reason unbalanced outs wouldn't be enough on their own?

There's several points on the board that can be used for unbalanced outs... and have enough oomph drive capability too.  It's a question of real estate space though on the rear panel and PC board. We'll fine tune it when I am closer to a final product.


Right now, I feel I'm doing 2 steps forward, 1 step back. :)
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Offline digifish_music

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Re: New TS-2 Preamp ... under development (part II)
« Reply #36 on: August 13, 2008, 09:15:21 PM »
Sorry, I can't put a battery inside. (Note, I'm not using a custom-made case where I can have every feature/opening/design/dimension made to spec to my liking. Maybe when I become big like "Grace" or "Sound Devices" :) 

There are portable batteries you can use though.





While no internal battery is not a show-stopper, not having a ready solution may be for some.  It would be nice to be able to purchase an AA battery sled to go with your pre, 8 x AA would give you a series/parallel arrangement of 6V with a decent mAh rating.

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Offline PH

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Re: New TS-2 Preamp ... under development (part II)
« Reply #37 on: August 13, 2008, 09:36:43 PM »
An internal battery? I see no need whatsoever for that. There are countless ways to easily power this unit.
Same goes for unbalanced outs or RCA jacks. Very few people would ever use them and I see no need to mess around with any sort of unbalanced output, ever.
Mid-side? Do it in post people.
HPF, same....but I would like this feature since ultra low lows have no real value in recording anyway.

Clean simple design is what you have already, stick with that and ignore some of the more ridiculous suggestions for features.
Cheers!

Offline su6oxone

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Re: New TS-2 Preamp ... under development (part II)
« Reply #38 on: August 13, 2008, 09:59:36 PM »
As a frequent stealther, I would love to see an internal battery and a 1/8" stereo out jack included so that you could easily hook this up to a R-09 or other recorder without XLR inputs.  This preamp looks really good though, can't wait for it to go into production.  8)

Offline tenesejedd

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Re: New TS-2 Preamp ... under development (part II)
« Reply #39 on: August 13, 2008, 10:01:08 PM »
An internal battery? I see no need whatsoever for that. There are countless ways to easily power this unit.
Same goes for unbalanced outs or RCA jacks. Very few people would ever use them and I see no need to mess around with any sort of unbalanced output, ever.


I disagree. There are many people here who run the edirol, marantz, and tascam hand held digital recorders, all of which have 1/8" inputs. Having unbalanced outs (1/8" or RCA) would make this very easy to use with such recorders. Again, not a deal breaker for most. If this already had an unbalanced output, i would probably end up buying one to run with my R-1 to run in addition to my FR2-LE

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Offline fivefishdiy

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Re: New TS-2 Preamp ... under development (part II)
« Reply #40 on: August 13, 2008, 10:14:19 PM »
Can you move the relay and meters off the split supply and just use the (unconverted) input voltage?  How how much are the relays, a few mA?

The VU meters are already off the split supply.

Yeah, I plan on doing the same thing with the relays... just power them directly via the 12VDC raw input.  power consumption? I can't remember now... but definitely I'm using a 12V relay... lower consumption than a 5V relay.


Internal Batteries

I'm not really going there. No plans to do that. Not with this case. Don't want people screwing/unscrewing/opening the case just to change a couple of 9V batteries inside. Maybe if a 9V lasts for months... but not for this purpose. There is a twin-9V battery holder that is available but A) No more space inside the unit.  B) expensive.  C) Need to route square holes to the rear panels (which there is also no more space) and which means more machining, which is also expensive.  Bottomline... It's a real expensive change to do and the upside is not very convincing for me.  I think a small external battery, hooked up to the locking DC jack is a more easier solution.

As for the battery sled, good idea.... I'd leave the implementation to some other entrepreneurial guy.
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Offline digifish_music

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Re: New TS-2 Preamp ... under development (part II)
« Reply #41 on: August 13, 2008, 11:33:29 PM »

Internal Batteries

As for the battery sled, good idea.... I'd leave the implementation to some other entrepreneurial guy.

I just found images of this AA to 7.5V battery sled (three units in the pic below), takes 10 AA's



That should last a while...just got to track down the manufacturer.

digifish

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Offline sanaka

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Re: New TS-2 Preamp ... under development (part II)
« Reply #42 on: August 14, 2008, 04:13:40 AM »
nashphil wrote:

Quote
An internal battery? I see no need whatsoever for that. There are countless ways to easily power this unit.
Same goes for unbalanced outs or RCA jacks. Very few people would ever use them and I see no need to mess around with any sort of unbalanced output, ever.
Mid-side? Do it in post people.
HPF, same....but I would like this feature since ultra low lows have no real value in recording anyway.

Clean simple design is what you have already, stick with that and ignore some of the more ridiculous suggestions for features.
Cheers!

I totally agree with Nashphil's last sentence here. Keep it clean and solid as a brick, don't load it with so many little thingys that the essence - the actual mic to line amplification - is compromised in any way.

However, I feel the low-cut/HPF is important. If bass or rumble is flailing your inputs, you can't regain that lost S/N in post. You have to not record it for it not to eat your dynamic range. So if the filtering can be done with no compromise to the actual preamp, it's crucial.

It seems that enough folks are running R09's or whatever with unbal inputs that if there's easy room for an 1/8" jack and that can be easily implemented with no ill effects, then yeah, sure. Otherwise, one can always build/aquire a special cable to run balanced XLR>unbal. But I'd leave it at 1/8" and not worry about RCA's. If one is running unbalanced anyway, it's very likely for stealth reasons, and 1/8" is stealthier than RCA. IOW, I'm snobby enough to feel that unbalanced doesn't deserve much investment in effort or case real estate :P

I for one would vote against internal batteries even if this were offered.

Peace,
Sanaka


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Re: New TS-2 Preamp ... under development (part II)
« Reply #43 on: August 14, 2008, 05:59:32 AM »
^^  :coolguy:

Offline flintstone

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Re: New TS-2 Preamp ... under development (part II)
« Reply #44 on: August 14, 2008, 06:18:24 AM »
Hosa makes versions of the "special cable" with two XLRF to 1/8-inch TRS.
Check out the Hosa YXF-247 (1 ft.) or YXF-302 (2 ft.) or XYF-305 (5 ft.).
Price is less than $20 from your favorite online audio merchant.

This cable works with all the small recorders I've tried, including the
Edirol R-09HR, Olympus LS-10, Marantz PMD620, and Sony PCM-D50.

The Hosa cables use a straight XLR and angled 1/8-inch. I'll see if
I can find a ready-made cable with right angle XLR.

Flintstone

 

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