Compression ratio question

[Tubebass]

Is it possible to reduce the compression ratio on OTA-based compressors like the Dynacomp?

[Mark Hammer]

Well you can certainly reduce the compression amount by increasing the value of the Compression pot or simply sticking a fixed resistor in series with it.  Altering the ratio, however, is probably trickier since you are talking about the same general responsiveness, just less impact when it does respond.

Certaily one of the things that produces the illusion of less obvious compression effect is the mod which changes the recovery time of the rectifier.  If it is fast enough, then compression is applied on a note-by-note basis to the initial peaks of everything you pick, rather than prolonged over the course of several notes on a riff-by-riff basis.  Again, only decreases the obviousness of the compression rather than being identifiable as somethiing like a 2:1 vs 5:1 ratio.

Really, I suspect it would be much easier to adapt something like the Orange Squeezer to specific compression rations since it operates as a true automatic volume control.  The 82k input resistor and the FET serve as the two legs of this volume pot.  You can vary the compression amount/ratio by altering either leg or both.  For instance, if the 82k input resistor is smaller in value, then large variations in FET resistance will have less of an attenuation effect than they would if the same resistor were, say, 100k.

[markm]

I think the O/S+++ attempted to do just what Mark is describing here however, I don't know just how successful it was.

[Tubebass]

That all makes sense. The OTA-based comp in question is a Korg CMP-1, which is pretty Dynacomp-like except that it uses an LM13600 instead of a 3080.It incorporates the recovery time mod as standard, on a slide switch.The reason for the question is that I can't find a happy medium between no squish, and too much squish and a lower ratio would probably help. I'm a live sound guy and have messed with the comps in our system a fair bit, so I at least think I know what I want! . Guess it's a good idea to ditch the Korg and try something like the OS, or maybe the LA Lite.
Thanks for the reply, Mark!
Thanks to you too, Markm.

[markm]

The Q&D Compressor may be worth a look too.
It offers quite a bit more control over the effect and being a sound guy, you guys like to twittle knobs don'tcha?? 

[Tubebass]

Knob-twiddling is our stock-in-trade..... we just have to convince customers that we know what we're doing!

[markm]

 

[Processaurus]

I did a write up and a schematic a while back on a clean blend mixer circuit for the dyna/ross comp that I'm sure would work for the korg, its similar idea to old studio tube limiters, sometimes there was a knob or switch to blend the clean in with the limited signal, and get "compression".  Worked well for me, it is a whole little circuit though, rather than a mod to a couple components.

[Tubebass]

Thanks, Processaurus! I'll open up the Korg and see if there's room for a little board. The Korg has an op-amp buffer so Vb is already present on the board.

[markm]

I have an unverified layout for the Ross Mixer from Processaurus if you're interested. 

[Tubebass]

I sure am interested, and will be happy to verify the layout for you!

[markm]

I sure am interested, and will be happy to verify the layout for you!

I will PM it to you tonight. 

[markm]

Tubebass....
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