Compressor advice

[sonolink]

I've been asked by a friend to build a compressor. His idea is a stereo brick wall limiter with only 1 button for the input, sort of like the LA-2A but without tubes, and with a Mix button for parallel compression. Before someone asks, I asked why no tubes, to which he answered "no tubes=no maintenance".....I guess it's a choice....
Anyway, can anyone give me some suggestion as to what I could build for him, please?

Cheers
Sono

 

[joaquins]

For brick wall I mostly prefer digital stuff (also no maintenance) which can play with complex algorithms to minimize distortion while having enough speed for blocking every single peak over the threshold. There are a few nice designs in the analog domain which really works as brick walls, much more complex than most other beast around and they tend to be pretty good in few applications, as I said, for brick wall I tend to use DSP rather than analog, even when working in a room full of really beautiful analog gear, capable of doing this at some extent. If what he wants is a nice bus compressor/limiter but he can live with some peaks out of it to clip or brick wall later the span is much wider. I would go with something with VCA probably as a general use bus compressor, peak/rms side chain, I really like what I have with my Symetrix in many many cases, but I only have one so never used too much in a stereo mix, I did used some other's to do so, but not so much. Sidechain has a few tricks but nothing impossible to build, I have the schematics, if you can't find them PM me and I help you with those.

LA2a is a rather slow compressor, no way to use it as a brick wall. If he's looking for a nice opto compressor like LA2A but without the tubes I wouldn't think much, LA3 is what he wants, LA4 if you want cheaper and easier to build, but more than one control available there... There are other opto compressors around and some of them are really good, many choices to make there.

The mix  could be made by a single small board available here around or you could make it pretty simple.

JS

 

[sonolink]

Thanks for your reply Joaquin.

My friend's mention of the LA2A is related to having few controls I think, not the speed or character of the compressor.  Maybe a LA3A as you say could be a good option though. I know Serpent Audio does a build. Do you know of any other. And are there other sources rather than UA, eBay or Drip for the T4Bs? Finally, have you ever built a T4B? Is it tricky?

Cheers and thanks again for the input
Sono

 

[JohnRoberts]

Check out THAT corp app notes.

JR

 

[Upacesky]

You can find new t4b in Europe at igs audio, Poland.

 

[hazel]

THAT4301can be used as subtle or limiter compressor,

You can use standard app note schematic, Threshold, Ratio and Gain controls, i'd add PEAK/RMS and HARD/SOFT KNEE switches

 

[sonolink]

Thanks a lot for the links guys. That THAT corp page is great!
I was thinking more of a kit kinda thing but still I'll check it out. The "One knob squeezer" sounds interesting.

The IGS T4B has a good price
Thanks Upacesky!

Cheers

 

[electric_diaries]

The "One knob squeezer" sounds interesting.

I built this recently as a stereo linked unit and while it does have a nice kind of glue I don't think it is the best choice for your friend’s peak limiter.

Firstly the it has RMS detection where as peak would probably be better for your friend. I would suggest trying some sort of peak limiter with the THAT 2180 or 2181. There are some design notes on their page and I think the 2180/2081 data sheets even have a basic design for a (theoretically) infinite ratio brick wall compressor which you could modify a bit.

Of course if you don’t have much experience then the SSL buss compressor would be a really great project to build for your friend.

For brick wall I mostly prefer digital stuff

I second this. I have tried for a very long time to design an analog peak limiter that can compete with DSP designs but I always end up preferring the digital. The only thing I found that did work really well was a delay circuit which allowed me to have look ahead compression.

 

[sonolink]

Thanks a lot for your advice electricdiaries
Much appreciated! I'll probably go for an SSL or a stereo LA3A
Cheers and Happy New Year!