[sdiy] State Var Filter with Nonlinear Feedback

[Scott Gravenhorst]

Ahhum...,  weakened attractors.  This makes very much sense.
I've noticed that getting chaotic behavior can be tricky.  
One thing I see in my schematic is a 20K resistor that passes 
a dry version of the feedback signal.  I think there should be 
a 500K to 1meg pot in series with that so that I can better 
control the mix of dry and distorted signal.  This would allow, 
I think, more control over how weak or strong the attractor is.  
Right now, I can change only the level of the distorted version 
of the feedback signal.

grichter at asapnet.net wrote:
>This is why it is called an "attractor" the function is attracted to stable
>points which are numeric multiples. Unstable intervals between the attractor
>points are the actual chaotic behavior. A good example is a flute, the
>"chiff" is chaotic behavior and the tone is when the energy settles into a
>stable attractor.
>
>It can actually be difficult to get at the chaotic behavior. Depending on
>the coefficients, the attractors may be so strong, the circuit will not
>operate in the chaotic mode. A solid tuned pipe has very strong attractors
>(tight seal on flute pads) as the pads become leaky, the attractors become
>weaker.
>
>> 
>> Watching the scope it appears to be 'locking' onto integral harmonics.
>> A square wave input might be converted to what looks like a square
>> wave which is amplitude modulated with 2 sine cycles for each 1/2
>> square cycle.  As you adjust Fc, all of a sudden, 2 sine cycles become
>> 3, etc.
>
>

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