SC-1 Mic Preamp Kit

[owel]

robd & mix-it-well,

The IO-Module add-on I'm creating will have DI input, and also vu meter buffering, and transformer hookups switchable in/out via relays among other things. Also thinking about LEDs for signal levels and clip indicator.

[lukejs]

I´ve seen the high speed mic pre from Jim Williams, and was impressed at the size, slew rate, distortion...etc....for such an incredibly small mic pre pcb...... Does your mic pre offer the same or better specs ? I realize that the hsmp is made for retrofitting console pre´s.... and maybe is not exactly in the same market you´re competing in... but how would you compare your pre to the HSMP... I could buy that for 125 bucks already made...... Since yours takes up a larger pcb board...I take it that less was compromised so it should sound better...... I hope ? I´m seriously thinking of buying 8, because I´m very close to buying a DAV BG8..... Sell me on your product..... would it smoke the Onyx pre´s I have in my Onyx console ? Thanks, LUke

[owel]

Originally Posted by lukejs

I´ve seen the high speed mic pre from Jim Williams, and was impressed at the size, slew rate, distortion...etc....for such an incredibly small mic pre pcb...... Does your mic pre offer the same or better specs ? I realize that the hsmp is made for retrofitting console pre´s.... and maybe is not exactly in the same market you´re competing in... but how would you compare your pre to the HSMP... I could buy that for 125 bucks already made...... Since yours takes up a larger pcb board...I take it that less was compromised so it should sound better...... I hope ? I´m seriously thinking of buying 8, because I´m very close to buying a DAV BG8..... Sell me on your product..... would it smoke the Onyx pre´s I have in my Onyx console ? Thanks, LUke

Luke, I'm not familiar with the HSMP. Can you point me to the url where I can read about it? I have not heard of the HSMP or an Onyx so I can't tell you exactly how it sounds compared to them.

And I won't go into dissing other products. There's plenty of great preamps out there, mannn that I wish to have. I'm just a little outfit trying to sell this kit to the DIY community based on it's own merits.

I´m seriously thinking of buying 8, because I´m very close to buying a DAV BG8..... Sell me on your product.....

I have one customer, who hasn't done any kit building before and got his preamp kit finished. He did a test stereo pair recording with his DAV 1U unit.

See if you can figure out which is the SC1 and which is the DAV.

FiveFishStudios.com - Mic Preamp, Power Supply Kits :: View topic - Fast and Dirty....

And if I may quote him:

So I've been running one of a pair of SDC's in crossed pair config through the SC-1, the other through the DAV 1U, panned left & right with levels matched as close as I can. I'm recording room ambiance which is a pretty tough test, tonal differences are very easy to spot. First impression is that they're very similar, noise levels are equally low despite the fact that the SC-1 is sitting on a CD case on the floor...

After a few minutes it becomes clear that the SC-1 is more immediate, better transient response I imagine. The high frequencies are more open, the DAV sounds _very slightly_ veiled by comparison. Otherwise I think I could make a stereo recording like this and most people wouldn't notice that 2 different preamps were in use.

So not a Neve, not that I wanted one (much)...I can wait for the output trafos!

Well done, owel. Once I'd got over my amazement that I was actually capable of building a preamp, I was very impressed by the sound quality.

And here's some mention of the SC-1 preamp kit on AnalogIndustries.com (which I think is Chris Randall's site?)

blog | analogindustries.com

And I quote on his site....

Now, keeping in mind that it's just initial tests, and I haven't used it on anything but my own voice, it seems easily on par with a good quality mic pre from anyone you'd care to name. It is by no means something that you could call either "warm" or "phat;" I have Telefunken, Neumann, and Averil pres that all exhibit both of those traits in spades, so I know from whence I speak. It is _crystal_ clean and clear, though.
I didn't have it in the best possible RF environment, as it is splayed all over my workbench, and hooked up with unshielded wire, but even then it is pretty low noise. I expect it to be essentially noiseless once I get it in a rack with proper shielding.
So I'll build the other one, and put 'em in a rack and wired correctly, then we'll give 'em a real workout, but for now I can say "easy build, clear sound, miles and miles of gain." Well worth the money.

slew rate, distortion...etc.

These are the specs from the manufacturer of the IC chips I used in the SC-1 kit.

Mic Pre chip
-------------
7Mhz bandwidth @ Gain = 100
19V/us Slew Rate
1nV/sqrt(Hz) input noise

DC Servo chip (after the Mic pre chip)
-------------------------------------------
8Mhz Bandwidth
20V/us Slew Rate
Fet Input
8nV/sqrt(Hz) noise

Balanced line driver chip (after the DC servo chip)
-------------------------------------------------------
15V/us Slew Rate
-101 dBu Output noise
Small Signal bandwidth = 10Mhz


And they say a picture is worth a thousand words. So this is the screenshot I did using TrueRTA software.



And here's some photos I took of the output as shown on my oscilloscope... Signal Generator > SC1 preamp > Oscilloscope

Shown are 22Khz, 100Khz, 200Khz, 300Khz, and 400Khz on the scope.

I want to apologize to you in advance, as the 400Khz waveform is distorted.

Mic Preamp Kit - Electronics DIY Projects PCB


And please keep in mind this is only a $99 preamp kit, so try keep it apples to apples in your shopping comparisons.

[lukejs]

Hello, and thanks for the info, Owel ! I downloaded that recording the fella did with the sc1, and the Dav.... then split the stereo track into two mono tracks so I could compare the two. It seems that the SC1 was clearer on top, but lacked the mid and bottom of the DAV... the DAV recording used a bit more gain also, so maybe this could account for this ? Anyway.... it was nice to hear a recording comparing...but what I´d really like to hear is an acoustic guitar recording with both those pres. The glass tapping was good to show how the harmonics were recorded... but I´d like to hear something I´m familiar with.... Could you post some recordings of acoustic guitars with your pre sometime ? Thanks for your DIY product !!
OH.. and the Onyx pre´s are from the Mackie Onyx line of mixers... the High Speed Mic Pre is from Jim Williams´s Audio Upgrades site.... check it out..the thing´s about 2 inches long...if that !! Jim Williams, I´ve heard .. has said that the DAV pre could be improved with THAT chips... as I recall...so maybe this is why your pre sounds clearer ? Yóu´ve probably met Jim from the gearslutz forum ? He´s always got some great advice on improving pre´s.....

[robd]

I plan to order some, based on Chris Randall's recommendation, as soon as there is a rack case. (If I were back in the states, I would have access to all the tools I need to make something like that, but my selection of tools right now is pretty limited.) I might wait for the I/o module, too. If you haven't got them by then, I will be able to compare them with the onyxes, cause I've got an onyx interface.

Ps. I saw that the mods in the works include a di, but usually piezo DIs are much higher impedance than DIs for magnetic pickups. Typically 5-10 megaohms. That's what I was asking about. In my experience, piezos sound like crap (even more than just the inherent crappy piezo sound) when they are run through a DI designed for magnetic pickups.

[Farview]

I just got done building the first of two SC-1 preamps. The power supply and the mic pre kits went together without any problems. The parts are very well organized and the PCB is clearly marked. If I can put it together, anyone can.

I haven't ever taken on a project like this before and it all worked the first time.

I still need to mount it on something so can use it and see what these things can do.

[owel]

Thanks Jay for the feedback! Great job.

Looking forward to hearing what you'll do with them.

robd: Check your PM.

[Mosby]

Owel,

just something you might want to consider, but possibly have a listing of arts that could be swapped out (IC, Op-Amps, transformers, etc....). There are a lot of tweakheads that would love to try adding some different flavors - and if you give them a listing it might be helpful.

For the record, I am intrigued.

[owel]

but possibly have a listing of arts that could be swapped out (IC, Op-Amps, transformers, etc....). There are a lot of tweakheads that would love to try adding some different flavors - and if you give them a listing it might be helpful.

I've tried the preamp with THAT 1510 and THAT 1512 chips. For the balanced line driver (using THAT OutSmarts Chips), I've tried it with THAT 1646 and THAT 1606 chips. All good. http://thatcorp.com/datashts/OutSmartsComp.pdf

I have not tried SSM compatible chips with this preamp, but if they're 8 pin DIP, I don't see why they shouldn't work. Personally, I haven't tried them since I don't have any laying around.

For the trafo, I've tried them using Edcor 600:600 output trafos. The 1646 are robust enough to drive 600ohm transformers, so no problems there. You can also try Cinemag, Lundahl, Jensen, St. Ives, Carnhill, Sowter, etc... as long as they're 600 impedance transformers.

[drvenom]

Man, I've been waiting on this baby for months. I will definitely jump on board once casing is available; I don't trust my self to make an attractive case!

[T.RayBullard]

Originally Posted by lukejs

H
Jim Williams, I´ve heard .. has said that the DAV pre could be improved with THAT chips... as I recall...so maybe this is why your pre sounds clearer ? Yóu´ve probably met Jim from the gearslutz forum ? He´s always got some great advice on improving pre´s.....

jim williams suggests upgrades, but for anyone to say authoritatively that "well do this to this preamp and it will automatically be better" is ridiculous. jim states things that sound better to him.ok..so what. it is important to note that better tech specs are just symbols and words/numbers....."better" is a nowhere answer..we each have ideas as to what sort of sound(s) we enjoy, and if you take joebob dickrandom's opinions as any sort of gospel , you deserve whatever aural hell comes your way. it is damned impossible to quantify "better"! ive purchased preamps that, on paper, were impeccable, only to find out many dollars later that they disappointed severely. (DACS/MIllennia that means you..). that was my own foolishness and I have learned a lot from it. the ADL 600 is another example. Plush, a person whom I hold in very high regard, loves the sound. ive had it for the past two weeks, and dont care for it at all, . anyway..

the most noble things that a body can do here:

1. don't give your damned advice unless you can fit the advisee with your ears...

2. quit taking and asking for advice on "better". it is absolutely idiotic. get the unit in question and use the damn thing. if you like it, it is better, if not it isnt. go figure. Weep for your own stupidity.

3. advertisers , please remove your head from your third point of contact and stop claiming to have quantified "better" as it it isn't possible. also please stop using terms like "analog sound" "straight wire with gain" "the new retro" "vintage sound" "neve legacy"and other perverse and noxious terminology that makes this site look more like a podunk used Yugo dealership than a place for info that is actually worth a damn.

4. go play in the road or make music. stop feeding the internet monkey. information highway my ass. Disinformation more like it.

[JB872]

Hi Owel

I was reading the diy section of your site and noticed you were working on a 312 mic pre kit. When will this kit be available? I'd be interested in 8 channels and a rack case.

[owel]

There's so many people selling 312-type preamps that I'm on the fence regarding this one.

But this circuit is also so simple (input trafo, opamp, output trafo), that it's also very tempting to do. However, cost-wise, it's going to be more expensive than the SC-1 because of the transformers. I'll need lots of mulah for my inventory... or maybe just provide a partial-kit and you buy your own transformers.

We'll see...I want to finish first my 1u cases and the IO-module I'm working on before I revisit and think more about this 312-type pre. Stay tuned.

[JB872]

There's so many people selling 312-type preamps that I'm on the fence regarding this one.

Really? Is there someone else, besides Seventh Circle, selling a 312 kit that includes a 2520 opamp?

But this circuit is also so simple (input trafo, opamp, output trafo), that it's also very tempting to do. However, cost-wise, it's going to be more expensive than the SC-1 because of the transformers. I'll need lots of mulah for my inventory... or maybe just provide a partial-kit and you buy your own transformers.

I'd still be interested in a kit, minus the transformers...but I'd need to know what transformers to buy and where to buy them from.

We'll see...I want to finish first my 1u cases and the IO-module I'm working on before I revisit and think more about this 312-type pre. Stay tuned.

Fair enough...PM me if you decide to revist the idea.

[Faderjockey]

Well I think that would reflect in the price.... If you make him do the research for you..

You can look it up and there are many styles of transformers you may or may not like. You can research and use what API used.. Or you can change it up a little and try different flavors. You may find a setup that works for the type of sounds you like best.

You can buy a couple different ones.. Try them in a kit test record them see what you like.. Then from there buy how ever many Ch's of kit you want, Then order the Transformer you liked best.

[kt66]

He said that there were many people selling 312-type preamps - not specifically kits.

The Seventh Circle A12 is a great sounding piece and is a pretty good deal in kit form - do we really need another choice for the same sound? Why not ask for something different...like Chandler TG2\Germ knock-offs?

[owel]

I have a 10% sale going on from today until the 17th.

Hurry, they're going fast.

[JB872]

He said that there were many people selling 312-type preamps - not specifically kits.

Sorry, I thought we were on the topic of kits.

The Seventh Circle A12 is a great sounding piece and is a pretty good deal in kit form - do we really need another choice for the same sound?

I guess it depends. How much does an A12 kit sell for? If you go to Owels site and check out his blog, he claims to be able to make these 312 pres relatively cheap.

DIY-Central.com - Go Create something! - PCB Design, Electronics - DIY API Preamp Project

I've also read a couple post here on GS saying that the A12 doesn't really sound like a 312.

Why not ask for something different...like Chandler TG2\Germ knock-offs?

I already own a TG-2 and a brand new API 3124 runs for $3000 up here in Canada. Plus, Wade at Chandler has helped me out of a couple jams and has priced his gear reasonably. But if you want a Chandler knock off, maybe contact Owel and see what he can do for you.

[owel]

The Profile output transformer I used for that API type circuit is long gone. Profile doesn't seem to make them anymore. Wish I bought a lot of those when they were available.... I think they were like $20 or $25 apiece back then a few years ago. (Profile stopped selling that model after a lawsuit by API from what I heard.... so it's probably the real deal.)

For the discrete opamp, I used a Melcor DIY (cost less than $10), or buy a $50 DOA from so many places.

Then you need an input trafo. So many choices... Cinemag, Jensen, Lundahl, Sowter, etc...

Is it an API clone? No. If you want an API sound, you'd need to use API part #s, and API transformers. Is it an API-type circuit? Yes. Will it sound like a real API? Probably not. But it will still be good.

Again, right now I have no interest in doing an API type pre. I waver between "not interested" to "maybe".... but I haven't wavered into the "definitely" I'll do it. It's just not on my mind right now.

[kt66]

Originally Posted by JB872

I guess it depends. How much does an A12 kit sell for? If you go to Owels site and check out his blog, he claims to be able to make these 312 pres relatively cheap.


I've also read a couple post here on GS saying that the A12 doesn't really sound like a 312.

The A12 kit sells for $284 plus the cost of the op-amp, which is a good deal if you build it yourself. Now, you cannot compare the cost of what Owel came up with for his little DIY project versus what he would be able to sell a complete kit for - I would bet it would end up being close to what the A12 sells for.

I could care less if a few people on GS say that the A12 does not sound like a real 312 - mine sound fantastic and I watched Michael Wagener use them on toms along with real API's (which he actually ended up using on the bottom of the toms with the A12's on top!). There are lots of opinions here on GS - with some being heavily biased for the stupidest reasons.

I am actually on the fence about ordering a pair of SC-1's at the moment. They look nice and I'm sure they sound great, but do I need more channels of clean gain? Owel appears to have done a very nice job on the design and from looking at the parts he is using, I think his prices are very fair. That said, when you start adding in the power supply, transformer, a chassis etc. it starts to add up - it can only be done so cheap.....!

My point was/is that if Owel were to come up with another kit, it would be nice if it were something different from what is already available. I just used the TG2\Germ as an example, but it obviously could be something else (though the TG2 is no more reasonably priced than a 3124 and some of us don't already have one).

[rapfreak]

Originally Posted by owel

I have a 10% sale going on from today until the 17th.

Hurry, they're going fast.

I just picked up a pair and it looks like his stock is WAY down. I'd suggest hurrying if you want one.

[DeadPoet]

I don't want to piss off anyone, or take anyone's business, but the described sound and function of this preamp resembles this little company: MICROPHONES LINE AUDIO DESIGN


Herwig

[owel]

I don't want to piss off anyone, or take anyone's business, but the described sound and function of this preamp resembles this little company: MICROPHONES LINE AUDIO DESIGN

Herwig

Why do you say that? Because I used the term "transparent", "servo" or something like that?

So what are you saying??? All the other preamps that call themselves "warm" also copied from each other?

"Electronically balanced input and output" is just a fancy way of saying "no, it doesn't have transformers" and a lot of preamp manufacturers are using this term too.

48V phantom power??? Every preamp worth it's salt has phantom powering.

If you're inferring I copied their design, I'd be happy to show you the link to the IC datasheets where this design is based from. The IC manufacturer tells you exactly how to use their part#. Go to BTSC Stereo TV - BTSC Encoders - Audio Technology and Analog Technologies; Semiconductors, Digital Signal Processing | Texas Instruments

So if anybody is doing any copying, it's everybody following the manufacturer datasheets on how to use their chips.

So if Lexus used the term "luxury, sports sedan, V8, 280hp engine".... did they copy their description from some little company known as "BMW" ? or how about "rugged sports utility vehicle"... did Chevy copied their description from "Ford" ?

[DeadPoet]

Please reread the first few words of my post...

I was just giving an alternative to your kits (and in Europe cheaper too) but now that I reread my original post I see it could come over in a different way (I'm not a native English speaker)




Herwig

[owel]

Just an update! Cases are coming together real soon.

The prototype front panel arrived... holes lined up perfectly... and most importantly, the gain marks line up PERFECTLY with the 12-step Grayhill selector switch.









Next step is manufacturing a prototype for the rear panel... but this should be easier than the front panel, since the dimensioning and holes are not as critical.

BTW, this is a (4) channel preamp case in 1u rack height.

I'll also be making an (8) channel preamp case in 2u rack height too.... that will be later.

[filthyrich]

1. Roughly..how much do you plan to sell the case for?

2. Is the front panel going to be drilled out for 2 pre's, 1 pre or drilled to order?

thanks
-rich

[Mosby]

Originally Posted by owel

Just an update! Cases are coming together real soon.

The prototype front panel arrived... holes lined up perfectly... and most importantly, the gain marks line up PERFECTLY with the 12-step Grayhill selector switch.


Next step is manufacturing a prototype for the rear panel... but this should be easier than the front panel, since the dimensioning and holes are not as critical.

BTW, this is a (4) channel preamp case in 1u rack height.

I'll also be making an (8) channel preamp case in 2u rack height too.... that will be later.

Well, crap man. Now I am actually going to have to buy one (I'm sure we're both oh so disappointed by that). Not I just need to find a good workspace (my crappy apartment probably won't cut it for the soldering - why do I feel like i'd end up losing my security deposit).

[stonewall40]

Can anyone report on how these sound out in the real world?
Thanks!

[owel]

2. Is the front panel going to be drilled out for 2 pre's, 1 pre or drilled to order?

The cases will be pre-drilled for (4) channels in a 1u rack height.

I don't have definite prices yet for the case, waiting for the production quote for the rear panels.