DIY Preamp kit

Farview

Farview

Well-known member
I just got done building two preamps from a kit.

Here is a gearsluts thread talking about it http://www.gearslutz.com/board/new-product-alert/134726-sc-1-mic-preamp-kit.html

This was the easiest kit I've ever built. Everything was clearly marked and organized. It all went together and worked on the first try. The preamps sound awsome. They are really clean and quiet, great for my SM7.

Here is a link to the guys site
http://www.fivefishstudios.com/

I built 2 of the SC-1 preamps and the power supply.
 
Are they better then the sytek, prosonus type of stuff? I need some clean high gain preamps with stepped gain knobs for stereo stuff.
 
He compares it to the BG-1 on his site, with not much difference between the 2. Since I have a BG-1, I will pass on this kit and wait till something with a different flavor comes along.
 
TexRoadkill said:
Are they better then the sytek, prosonus type of stuff? I need some clean high gain preamps with stepped gain knobs for stereo stuff.
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I don't have Sytek or Presonus preamps. I just got them together yesterday, I have a session today that I plan to use them on. I will ask for permission to post samples.
 
Do they have a rack mount box available? I just took a quick trip around the site and didn't see anything... looks like they might fit vertically in a 2u frame?
 
There is no box available (yet?). You would need to get a 2 space rack box and start drilling. (the transformer is too tall for a 1 space box) You should be able to fit 8 of these preamps in a 2 space rack.
 
http://www.studio-central.com/phpbb/viewtopic.php?t=44938

owel said:
These Panasonic electret mics are $.86 apiece at digikey.com. 20Hz to 20Khz response. It just needs one resistor and cap to properly bias it for operation. Add a few more dollars for the XLR connector and you have a mic.

Even at $20 apiece, it's way overpriced for what it does.
Click to expand...

I wonder if now that he's put a commercial product on the market, he has a better appreciation of what it takes, and what it should cost in terms of parts vs. labor . . . given that I doubt there is $99 of parts on that board, and it's a kit, I expect an apology sometime soon :D
 
I looked and maybe missed it, but what's the pre input impedance. also, the instruction PDF did not have the schematic... is schematic included?
 
Sonixx said:
I looked and maybe missed it, but what's the pre input impedance. also, the instruction PDF did not have the schematic... is schematic included?
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He sends the schematic and parts list with the kit. I'll have to look and see if it says anything about the impedance.
 
Here is a quote from a thread on Studio Central
I wish I can show you a complete spec listing.

I inquired and got estimates of $1000+ just for a one-time TESTING of the pre and me getting printed specs of the result. I can't afford that kind of cost at this early stage in the company... maybe someday...

This is a one-person project, from design, testing, prototype, development, inventory, manufacturing, packing, shipping, and customer support! <whew!> I don't have the resources to do that kind of spec sheet yet.

Now, I do know that the SC1 is also electronically balanced, optimum mic impedance of 150ohm or so, can go down to 10Hz and flat to 20Khz, and can go up to 300Khz at maybe -6dB. Has SEND and RETURN unbalanced, Servo balanced, RF Filtered at both inputs and outputs, +6 to +72dB gain, the output driver I'm using is capable of +27dBu, 18Vrms into 600ohms. Those are the things I know... I don't know yet the EIN, actual CMRR, etc... like I said, I'll need to pony up $1000+ just to know those numbers.
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EIN is fairly easy to test, as is CMRR. For CMRR, just send a common mode signal to the pre, and see how much it drops. For EIN, strap a 150 ohm resistor across the input, measure the output noise, adjust for gain, and subtract the thermal noise of the resistor (-132dBV if memory serves). However, that stat could be affected by the case, so with the bare PCB it could be inaccurate.

I can't afford test labs either, but you can get pretty close to accurate if you compare your circuit with known and trusted gear.

Also, the output driver might be capable of 18VRMS, but if your PSU is +-18V, you are limited to about 12.7VRMS, or +21.5dBV/23.8dBu, assuming your signal chain is close to rail-to-rail performance. Since that output would clip nearly any converter, in digi-land that is somewhat academic.
 
Farview said:
There is no box available (yet?). You would need to get a 2 space rack box and start drilling. (the transformer is too tall for a 1 space box) You should be able to fit 8 of these preamps in a 2 space rack.
Click to expand...
Or just source a torroid that will fit into a 1u case.

Seems silly to put two of those little things into a 2u case. Well, it does when you're as rack space restricted as I am! :D

He reccommends Digikey part# TE62065-ND on his forum, I guess any 20-0-20v, 25va torroid with dual primaries and secondaries would do it.
 
Anybody got expirience with some discrete mic preamp which has schematic available?
I would like to build some, but don´t know which, and I also have a little problem with chips that are not available in shops.
Any suggestions?
 
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