More Nonlinear

[Sean Costello]

Scott Gravenhorst wrote:
> 
> Ok, this weekend is "nonlinear feedback filter mad scientist" weekend.
> I've decided on a state variable filter because it can be converted
> easily to a simple single pole LP filter with an SPST switch.  It also
> has two feedback paths to mess up with nonlinearities.  I've come up
> with 5 or 6 simple nonlinear devices that I can patch in to test.  I
> will be using an LM13600 for the OTAs.  For now, I will control the
> nonlinear stuff with a simple pan pot to pan between a linear path and
> a nonlinear one or maybe two different nonlinear paths, but if it
> sounds wierd/good, I will eventually devise some kind of VC panning
> system.

Cool!! Keep us posted!  My one request: try a full-wave rectifier in one
of the feedback loops.

Question:  Doesn't increasing feedback in a state-variable filter
actually increase the damping (i.e. less Q)?  If so, the effects of
nonlinear feedback in a state variable filter might be very different
than nonlinear feedback in a Moog-style filter, or a Sallen-Key filter.
Man, I need to get that Electronotes 4-pole filter running again, so I
can put circuits in the feedback loop.

Sean Costello