[sdiy] tanh distortion in a filter

[Harry Bissell]

The 'sine shaper' only works at one particular input amplitude. Too low, it does not distort, too high
and you get a square wave anyway. I was thinking it could be 'good' for a filter but then changing
input amplitude changed my mind.

In fact, I think I have seen (am seeing) an effect where an LPF works 'better' with a higher input, and
as the input decays, the overall cutoff seems to go up (higher center frequency). I theorize its that
'sine shaping' that is somewhat inherent in the OTA filter makes the LPF better at higher amplitudes, worse
at lower amplitudes.

anyone adept at math-fu please propose any alternate explanation for my observation... 

The Moog ladder is of course famous for its sine-shaping overdrive characteristic...

H^) harry


----- Original Message -----
From: David G. Dixon <dixon at interchange.ubc.ca>
To: 'Olivier Gillet' <ol.gillet at gmail.com>, music maker <music.maker at gte.net>
Cc: synth-diy at dropmix.xs4all.nl
Sent: Wed, 13 Apr 2011 19:09:34 -0400 (EDT)
Subject: Re: [sdiy] tanh distortion in a filter

> > What does it do?  (as in what does it sound like?)
> 
> Slight fuzz / soft clipping.

So, is anybody here going to answer my (potentially stupid) question about
using a sine shaper as a preamp, or am I just going to have to wire one up
and try it myself?  Sine shapers are essentially tanh operators, are they
not?  This could be done with a differential pair or an overdriven OTA.

_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy

-- 
Harry Bissell & Nora Abdullah 4eva