any small colored compressor to built? (old Telefunken, Neumann or Siemens comp)

Hi everybody !


... I was wasting my time on ebay looking for an old and cheap compressor, that would sound very colored (I already have a pair of symetrix 501, a GSSL and a Bellari RP583 which is ery colored).
I found some LA12, Valley Audio Dynamite, and one Telefunken U373... then I made some research about all those little German compressors, that seems to be nice gears, but I don't have any idea of how it sounds ! The only German comp I ever heard is the EMT 266, which I loved, kind of smooth and colored sound, "woody" when input gain is high.

So, the question are:

- how does sound those Telefunken, Siemens or Neumann old comp (U273, 373, 473 , etc)?  (-> if somebody has audio samples , please  )
- would it be esay and cheap to copy ?
- what kind of other coloured, creamy, squashing compressor would be ok ? ( any DBX 117/118/119, or more obscure things... ?)

thanks a lot for your advices !

Well, I've just completed a diy version of the UREI LA-4 compressor and it sounds absolutely fantastic in my ears. I can highly recommend it.
Hang on for a few weeks and I'll have a batch of boards ready. I'll announce it in the Black Market... I'll post the layout and BOM before that here.

hum... interesting Luny ! how much do you think it will cost for a complete and finished LA4 ? ... here I'm looking for something small, cheap and easy to do...

I can recommend the Neumann U473, but I wouldn't call it colored, since it isn't.
like most other Neumann modules. they are just clean, and do their (great) job.

I don't think this is an easy one to copy, even with the VCA schematic we have.

Always wanted an la-4
updated I.C.  ?
xfmr i/o ?

1:1 Clone except for:

2 x NSL32 opto. (Have ordered parts to make the original type but the NSL32 is so close that I'm only doing that for nerdy reasons.)
BD139 and BD140 power transistors
TL074 compatible pinout (means MC33079 compatible too)
And the output transformer is off board so you can use any you like. (Mine has a Cinemag CMOQ-2S output transformer and I think it sits right where it should in a mix.)

Other than that it's exactly like this schematic:
http://www.waltzingbear.com/Schematics/Urei/LA_4A.htm

There's some subtle changes in the design between the blackface and the silverface version. Some of them seem to be improvements and some seem to just be different. As far as I can tell by experimenting and comparing results with test files forum user Craptical was kind enough to make for me with both the silverface and the blackface, it's mostly a matter of adjustment, the optos, the output transistors and possibly the 846 opamp used in the blackface.

These differences are extremely easy to test and try out with the board I'm making. Would mean a couple of jumpers instead of the two 47Ω resistors by the output transistors, a couple of caps added (maybe to the copper side), maybe pinout for the 846 is a bit different...I don't know that chip yet.

However, I think we nailed the sound of it and in my opinion ours sits between the blackface and the silverface I've heard being closest to the blackface. I'm still figuring out the best way to adjust it and I'm 100% confident that no one would ever be able to tell our clone from the real deal if they didn't know which was which.

This far I've tested a few optos to find the one that matches the blackface best and though the VTL5C4/2, which to my knowledge is the one JBL recommends as replacement for the original optos, does work, in my opinion it creates a slightly different character. The buzz/distortion, that lower frequencies introduce and which sound particularly awesome through the blackface, sounds less awesome with that opto. So far the best opto for the job is the NSL32 which in my opinion gives the same buzz as I hear through the blackface.

It's all complete with stereo link option and everything... I even included the female phonojack for it on the BOM.

Anyways, I'm working to get the layout ready for the factory. We're not having that many boards made to begin with but we'll consider having more made if there's a great deal of interest.

I'll post the layout and the BOM soon so anyone who can make their own boards can dig into it.

Wow !!! great job Luny !!!

I don't know if i'll have enough money for this ... I just finished two pairs of API preamp (800€ ouch my bank account  ) but I suppose the most expensive will be the transformers, right ?

[silent:arts]

I can recommend the Neumann U473, but I wouldn't call it colored, since it isn't.
like most other Neumann modules. they are just clean, and do their (great) job.

I don't think this is an easy one to copy, even with the VCA schematic we have.

Click to expand...

okay, so if it's clear... and complicated to build, let's have a look to somthing else 

What about a simple FET design, such as the SSL talkback comp ( .. I previously posted here for making a copy of the Ridge Farm Boiler.. desgined for the SSL talkback comp), or any little comp with just some FET ?

The Cinemag CMOQ-2S is under $30. It sounds amazing in the output of a 1176 and I used it here because of the somewhat similar output stage. (I don't know all that much about it, it's pretty much a lot of guesswork on my behalf.) Maybe you can find something even cheaper and still sounding great. An OEP A262A2E maybe? For now I recommend something to step the output down a bit. The gain through this baby is insane.

It's not at all an expensive project. I believe that if you go for a cheap meter, leave out the option for switching to +4 and +8 VU mode thus saving money on the switch (who needs that anyway?), grab the cheapest box to put it in...you could solder it up as a fixed 4:1 comp which is probably how you'll use it the most...come to think of it; Leave out the meter entirely!....then you could be up and running for approximately €120, I think. Probably less.

Then just upgrade it with the rest of the features when you got the cash to bring it up to the standard you want. ;D

120 € is really cool !! I think 150 is still Ok, and you're right, CMOQ2 sounds very beautiful, this is what I've got in my API preamp, I do love the sound ! .. but why not change of output transfo and try those OEP ones, if they have a different colour, this would allow to have another sound.
Fixed ratio ? mmm a rotary swtich is not so expensive, and for the meter I can have some for cheap.. the most expessive will be the case  ;D
Thats a pretty cool project !!

just a stupid question, LA4 is .. mono ? lol so, i'm surprised that this would be so cheap.. the price in shop is more around $800 than $150.. why so much difference ?

The brand.

With regard to the few cents saved on the switches and so on...well, I don't know HOW tight your budget is.

It's mono yes, but with VERY easy stereo linking.

And you could easily have two boards in one 1U case. There are no tall components on there and two Anders Electronics C220VU meters will look just fine. In all that would mean two small meters, 8 knobs and two on/off switches on the front panel. (6 knobs if you leave out the two meter switches.

hmmmmm, another interesting DIY project, especially since it can be done really cheap...... aaaaarrrrrgggghhhh !