Rock Face Question

[mac]

I gave the rock face a try. But I swear I can hear some kind of "compression" or similar mainly with long decay power chords.
My guess is that the opamp forces C2 to 4.5v, regardless of the source of the deviation, temperature or AC signal.
The relaxation time is large but after a few seconds, when you let notes decay the servo begins to oppose to AC.
I suspect the 10uf caps set the time constant.



mac