Simple compressor for complete squash

[Taylor]

I am working on a pitch shift-octave type thing, probably using the front end of the OC-2, and I'd like to have a compressor in front of it to improve tracking. It doesn't need a lot of controls like attack and release time, knee and so forth. I just want something that squashes the signal heavily and has a low parts count, since this is just a small building block in an ever-expanding circuit.

Any suggestions?

[earthtonesaudio]

http://www.diystompboxes.com/smfforum/index.php?topic=41768.msg368462#msg368462

Edit:  I read on to a later post in the same thread, where Brett posted this which is simpler and supposedly better:
http://www.diystompboxes.com/smfforum/index.php?topic=41768.msg374442#msg374442

[Mark Hammer]

T'wer I, I'd want everything I could drum up working in favour of whatever is supposed to be deriving the fundamental.  Part of what that means is making sure that the harmonic balance does not shift over the lifespan of the note.  Unfortunately, because compression normally aims for the overall amplitude and not simply the maintenance of level for one part of the note, there is increased risk of mistracking.

So here are some things to explore:

1) Filtering: If you're going to try and maintain some high average overall level, make damn sure those pesky highs and lows are nowhere to be found in any signal about to be amplitude controlled.  So, a 2-pole highpass to eliminate any possible hum or bass artifacts leaking is good.  A 2-pole lowpass to shave off most of the harmonic content is also good.

2) Clipping: Boosting and clipping signals is another way of maintaining a relatively constant average signal.  And as so many of us can attest, lotsa gain coupled with lotsa filtering can often get you something that sounds for all the world like a triangle or sine wave oscillator....which any pitch detector will like very much.

3) Squelching/gating: Crossover distortion can be your friend here.  Remember that when a diode pair are in series with the signal path, nothing gets through that isn't over the minimum signal-level threshold.  So a back-to-back pair of Ge diodes prior to and after a more typical TS-type clipping stage may be able to keep any "misleading" signals safely away from your fundamental detector.