scream

[Sean Costello]

mbartkow at ET.PUT.Poznan.PL wrote:

> A more general (and somewhat "academic") approach would be to build
> a possibly linear state var. filter and insert various nonlinearities
> into the feedback loop. Such structure allows for crazy experimentation
> which is not limited to symmetric or asymmetric clipping/soft saturation,
> e.g. something similar to Serge waveshaper.
> 
> As far as I remember somebody mentioned his experiments with various
> distorting elements within SVF. I would be glad to hear more about
> what kind of sonic effects may be obtained.

Dan Slater wrote about such circuits in a recent (Summer 1998) issue of
the Computer Music Journal. The circuit he described was named something
else, but it was essentially a state variable filter with a nonlinearity
(x to the 3rd power) in the feedback loop.

I am going to be coding the state-variable filter into Csound soon (the
Chamberlin topology, as it is called, due to it's description as a
useful digital filter structure in Hal Chamberlin's Making Music with
Microprocessors). It would be trivial to experiment with various
nonlinearities in the feedback loop. Unfortunately, nonlinearities in
feedback loops in the digital realm aren't nearly as nice as feedback
nonlinearities in the analog realm - in the digital world, you get all
sorts of aliasing, clipping, amplitude growing without bound, etc.
Still, I'll give it a try, and report the results.

Sean Costello