[sdiy] Synthancon VC-Resonance

[René Schmitz]

harry bissell wrote:
> The queerest thing about the sallen-key filter is that when the 
> resonance starts...
> it starts at the zero crossing instead of the peak of the waveform, like 
> Moog ladders
> and SVFs do.
> 
> I ~wonder~  why that is. It could make a big difference in the sound, 
> especially in not
> clipping later stages...

Its not the Sallen and Key topology per se.
In the MS20 the reason for that is that the gain is dependant on the 
amplitude. Those diodes in the feedback amp reduce the gain gradually to 
1 for amplitudes above ~2.1V, so an oscillation cannot be sustained with 
a higher amplitude. (Run smaller signals through this, and you'll find 
the resonating peaks "where they belong".)

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159