AW: [sdiy] [partly off topic?] Nonlinear Filter E.Guitar Test

[Nils Pipenbrinck]

Scott Wrote:

> One other thing:  I'm not exactly sure how this is
> happening, but I swear there are times when this
> box has pitch or frequency shifted (not sure which)
> the attack portion of a sound when I have it plugged
> into a monosynth.  ....


Some month ago I build a little state variable filter (for experiments).
Nothing fancy, not even voltage controlled. The basic 3 OpAmp design.

Beeing a guitar player I started to add a diode here and there, and added
more and more strange feedbacks to the filter.

Then - to my surprise - it started to do the same effect as you described. I
was able to hear pitch shifting and octaving effects. They where also
sensitive to the input signal. The lower the input signal was, the lower was
the octaving effect. If I run this circuit with a hot signal it started to
jump from one overtone to the other. Very very strange.

I don't have the circuit for it however. It was just an experiment on my
prototype board.

	Nils