Ideal DIY Preamp for passive summing mixer external gain stage?

I have sucessfully built my passive summing mixer and the GSSL too!
Now I need a clean, transparent and true "mic" preamp to finish my master audio chain... Of course it is going to be DIY. Which one do you recommend? I'd like to stay away from tubes because I don't feel confident yet to work with high voltages and I need something less colored. Any suggestions? I'm thinking of the SSL 9K or the green pre, although I'm leaning in the ssl direction. Is it difficult to build?

ytsestef said:

I have sucessfully built my passive summing mixer and the GSSL too!
Now I need a clean, transparent and true "mic" preamp to finish my master audio chain... Of course it is going to be DIY. Which one do you recommend? I'd like to stay away from tubes because I don't feel confident yet to work with high voltages and I need something less colored. Any suggestions? I'm thinking of the SSL 9K or the green pre, although I'm leaning in the ssl direction. Is it difficult to build?

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I'd stay away from SSL or anything with ICs for this scenario. The whole idea of a passive summing stage is to color the sound (in a similar way a vintage API or Neve console would do) . I use Martin's EZ1290's a lot. Anything Neve-ish will sound nice. A REAL tube mic pre (no IC's!!!!) will also be cool. Trust me, you want to stay away from "clean". If you want clean, you're better off summing inside the box. Hope this helps.

Dan P.

Dan - I think the 9k is a good suggestion, nothing wrong with "clean" and "summing in the box" is
VERY different, it's about your D to A calculating a "bazilion" numbers when outputting EVERY track
to a stereo pair, rather than having separate bass / drums / gtrs etc from their own outputs.
( less calculations and less artifacts = clearer image )

Coloured sound is great .... if that's what you want and you like "that colour"

Best option :
Passive summing box and keep the "gain make up" stage separate, then you can try either
the 9k or an API/ Neve or a tube stage at te back end

MM.

Thanks a lot for your answers!
I have already finished my passive summing mixer, so it will be a seperate unit anyway. Actually the resulting chain will be the following: Cubase 5 -> M-audio Profire 2626 -> Sonic Core A16 Ultra (16ch D/A Converter) -> DIY 16ch Passive Summing Mixer (40dB loss) -> SSL 9K Preamp -> GSSL -> Back into the audio interface and DAW.

I might try some neve type preamps too, but for now a have to mix a pop/rock album and I need something natural as a first approach.

However I have a few questions regarding the SSL 9K, as my build doesn't have to be that complex. I don't need +48V and I think I might get away with two 2Pole-6Position Lorlins for gain switches with rough gain steps, like 10dB, I don't care (after all I can still finetune the gain using the GSSL's threshold and makeup controls).

What do you think? And where can I get detailed answers about what changes need to be made? I can't seem to find an SSL 9K Help Thread in the Meta (the link is broken).

Thanks a lot!

ytsestef said:

I have already finished my passive summing mixer, so it will be a seperate unit anyway.

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Awesome! I would love to see some pics.

Yes, I will post some, but I need to get everything ready first so that I can post pics of the passive summer the gssl and the 9k at the same time along with some audio samples in a new thread discussing the actual improvement over ITB mixing. I hope in 3 weeks everything will be ready if I manage to get any help regarding the ssl 9k.

Part of the concept of passive summing is the ability to choose different recovery amplifiers for different sonic signature. I suggest you borrow or steal as many different pres as you can and forge an opinion as to what you like or dislike and eventually will use.

abbey road d enfer said:

Part of the concept of passive summing is the ability to choose different recovery amplifiers for different sonic signature. I suggest you borrow or steal as many different pres as you can and forge an opinion as to what you like or dislike and eventually will use.

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This is true. My only addendum would be the main concept of passive summing.... Passive summing is brilliant because it easily allows you to change the sound in a similar way it would change if you were to go from console to console. Again, I would say AVOID "clean" mic pres, especially if you like, for example, the sound of vintage API and Neve consoles.

just to get you boys back on track, the OP is looking for something "clean and transparent."  As Abbey said, ideally you will find a way to borrow/rent some equipment to test out various pres before you build something and are "stuck" with it.  I guess you live in greece?  I know I've seen other greeks around (member Vas comes to mind but I'm sure there are others). Maybe one of them is near you and would loan you an SSL (or API or Neve or all of them) to try and maybe use on this session while you decide what to make for yourself and gather parts for it.

good luck

There are several mic preamp chips (like from THAT) that could be used. You could eliminate the phantom power front end, and eliminate the variable gain pot to make something simple and clean.

JR

Well this is nice of you mitso but while I do like the sound of transformer-based preamps and circuits, I am sure that right now I need something clean. I can definately see me having the SSL9K, a 1072/73 and an API in a year from now, because I find this stuff cheap to build (when compared to the quality of the outcome) so, it's a sure thing I will be building all of them during the winter. So why shouldn't I start from the one I need right now?

Besides, my theory (and a lot of other people's as well) is that when you have only ONE, it better be neutral. When you have two, it can be one neutral and one colored. I have nothing against color and character. I just think that the faithful/neutral/transparent circuit will always come in handy no matter what. It has to be around in the studio. So why not start from it and later get some other choices too?

That said, I completely realize that when I build my API I'll probably be like "THIS IS THE SHIT!!!" and patch it in the end of the chain and leave it there forever  ;D ;D ;D

I hope I made a point  

http://www.groupdiy.com/index.php?topic=30026.msg363956#msg363956

If you want clean, Mikkel's THAT 1512 based pre is great. The PCBs are very small, so you could mount them inside your passive summing box as the default summing amps, and include jacks to go external into whatever more colorful preamps you lay hands on.

Having said that () I have used the THAT preamps with my passive summing box and much prefer my NYD OneBottle or Tamas FETBloke preamps for summing amp duty. I wish I had been able to afford a second Neev1272 clone, because the one I have is just stunning and a pair as summing amps would be so sweet.  8)

Is it the one called "ThatMic" ? Wow, this is CHEAP! And simple, too.
I was almost completely convinced to build an SSL9K until I saw that.
Anyone knows how does it compare to the THAT in summing amp usage?

Thanks skipwave!

I have a couple of "That" based pre's that I did on stripboard and they are very good.

I don't really want to get deep into "sound" opinions but they are "cleaner" than the
9k's I have, so if you want just "sterile gain" then go for it.
Personally I prefer the 9k's.

IIRC - DAV BG-1 is based on a "That" chip

MM.

MartyMart said:

Personally I prefer the 9k's.

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Figures.
It is only natural and expected the fact that most people would choose the 9K over the "That" preamp anyday.
Even without having heard it yet, from what I'm reading about it here, I think I'm gonna love it!

My preamp doesn't have to be exactly "sterlie", like 100% precise and neutral, just a very good sounding preamp that does not color the sound (at least not as much as transformer and tube designs do).

You know, maybe I'm swinging and missing, but what I would do is use the GSSL makeup gain. My GSSL was set up so that the makeup gain is still active when the unit is in bypass. In that case, you have a pretty decent sounding stereo recovery preamp with no phantom power.

Is this a stupid idea? 'Cause I'm about to build a passive summer and would like to do it this way...

jasonallenh said:

You know, maybe I'm swinging and missing, but what I would do is use the GSSL makeup gain. My GSSL was set up so that the makeup gain is still active when the unit is in bypass. In that case, you have a pretty decent sounding stereo recovery preamp with no phantom power.

Is this a stupid idea? 'Cause I'm about to build a passive summer and would like to do it this way...

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The idea is not stupid but it all comes down to Ω. Will the output Ω of the passive mixer be able to feed into the GSSL without issue? secondly will the GSSL have enough make up gain to bring you back to line level to go into your converter?


My two cents when it comes to passive summing is that the make up amps should be tube because tubes sound better when handing complex audio information. Plus IMO their harmonic distortion characteristics are sonically superior to anything solid state. However we are not trying to distort signals here just bring things back up to line level after going through passive summing. I highly suggest you look at the NYD one bottle. It will have enough gain to get you back to line level and sounds great. it's an easy build as far as tubes go. Don't let the high voltage worry you, because the amps are what kills you. It only takes a few millivolts to stop a human heart. Also by the time your poking around in DIY land your usually on the DC side which will bite you and it will hurt a little but nothing permanent. If your really smart you poke with other things that are none conductive so you don't get bitten by DC or AC if your on the AC side. But all in all if your careful it's never really a problem anyway.

pucho812 said:

My two cents when it comes to passive summing is that the make up amps should be tube because tubes sound better when handing complex audio information.

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Even though the vast majority of music made in the last fifty years has gone through hundreds of stages of humble op-amps?

-a

Andy Peters said:

pucho812 said:

My two cents when it comes to passive summing is that the make up amps should be tube because tubes sound better when handing complex audio information.

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Even though the vast majority of music made in the last fifty years has gone through hundreds of stages of humble op-amps?

-a

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that is true and I am not knocking op-amps at all, To do a large console would need opamps as using tubes there would just be difficult to handle, hell even a small console you need them but if your just  doing 2  preamps for make up gain, one for left and right, try tubes.

A quick observation... If the euphonic sound of tubes was that they somehow handled complex music waveforms better (?), what does better mean? If better means more accurately than opamps, the tens of opamp stages following would surely undo that accuracy. However if the tube stage "adds" coloration (distortion) that people like, that coloration will be faithfully reproduced by following opamp stages.

I held my tongue about a recent post in another forum where they suggested adding resistors from one supply to the opamp's output to bias the output into class A. If they just do this in the preamp stage (of a console) what about the rest of the console? I didn't say anything because I was fearful some phool would read it and decide to bias every opamp in his console?? I hope they have a strong PS and fan cooling.

Passive summing offers the false promise of not involving active circuitry. Make up gain is indistinguishable from active combining, and coloration could be added there, if it really was considered desirable.  I am kind of a straight wire with gain guy, myself. Intentional coloration IMO should have a bypass switch, so you can listen for the effect.

  JR