[sdiy] OTA / JFET as buffer of a Moog filter

[Richie Burnett]

Theoretically the symmetrical soft-clipping of the OTA should contribute odd 
harmonics (predominantly 3rd) to the sound, and the asymmetric curve of the 
JFET should contribute even harmonics (predominantly 2nd) to the sound. How 
much this affects the sound in practice will depend on how strong the signal 
is when it meets each non-linearity. The overall effect also depends on 
whether the non-linearities are inside the feedback loop or outside when 
feedback is applied around the ladder to produce resonance. Negative 
feedback is very good at "linearising" systems (that's why it's used in most 
audio amplifiers to reduce THD) so any effect is likely to be most 
noticeable with low resonance settings _IF_ the non-linear elements are 
inside the filter's feedback loop.

-Richie,

-----Original Message----- 
From: Florian Anwander
Sent: Thursday, August 07, 2014 10:11 AM
To: synth-diy
Subject: [sdiy] OTA / JFET as buffer of a Moog filter

I am not very much into moog filter theory, but I found that this about
the Moog Subphatty 37 might be a bit interesting for you:

http://www.youtube.com/watch?v=DYzsz2U7RM0#t=101

(starting from 1:40)

Florian
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