A simple compression pedal

[Fors]

Hello,

I just found this on my old computer, and remembered that I was thinking about compression using a simple op-amp feedback topology about a year ago, so I came up with this circuit and saved it for a future project.



And I now think the time for that future project has come, so I will soon be breadboarding the basic structure of the circuit to find the right component values, and (hopefully) update this thread as I go along. Have any of you built a compression pedal using a similar topology? Thoughts?

Cheers!

[samhay]

The Rothwell Lovesqueeze (http://revolutiondeux.blogspot.co.uk/2012/06/rothwell-love-squeeze-compressor.html) uses a similar non-inverting gain stage with a FET. It has mixed reviews. Your envelope follower is a bit different and I am not sure I quite have my head around it yet. Looks like something that should be fun to play with on the breadboad and will be interested to hear how you get on with it.

[PRR]

> Your envelope follower is a bit different and I am not sure I quite have

Ass-uming the second opamp is a unity-inverter, it's a plain full-wave rectifier. Small advantage over a half-wave; often moot in small audio.

No DC biases are shown, and in this type circuit, it matters.

The output limit-level is V(off) plus a diode. For most likely parts, this will be a lot larger than guitar level. Alternatives are a pad at the audio out, or more gain in the sidechain.

[merlinb]

 A similar idea is explored here:
http://sound.westhost.com/project67.htm