[sdiy] Non-linear properties of SSM2040

[rburnett at richieburnett.co.uk]

> The spectral effects on a sawtooth pushed through a non linear filter,
> without any resonance are impressive by themselves by the way. I never
> knew the effect of an analogue filter could be this substantial.

Yes, I found that the effects of non-linearities were greatest for the 
"zero resonance" case when I looked at the TB-303 filter in some detail. 
  When you turn up the resonance control the global negative feedback 
applied around the filter stages does a good job of linearising the 
filter.  So, it was actually easier to nail the high-resonance sound 
with a digital model than it was to nail the zero-resonance sound!

-Richie,