Topic: Greetings... my new mic preamp.

[digifish_music]

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: 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: 80/160 Hz @ 12 dB / Octave
while the 442 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

[sanaka]

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 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   I don't think the Aerco has a low-cut, yet remains highly respected, for instance.

Peace,
Sanaka

[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

[sanaka]

Here's a revised image, just because I get off on doing this. Sorry to be all post happy.



Peace,
Sanaka

[stevetoney]

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.

[stevetoney]

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.

[stevetoney]

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. 

[fivefishdiy]

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?

[halleyscomet8]

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.

[stevetoney]

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.

[fivefishdiy]

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).



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... 

[stevetoney]

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?      

...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!!!!

[landshark]

"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>

[anechoic]

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

[anechoic]

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?