[sdiy] Later MS-20 filter with 2164

[David G. Dixon]

> I'd have thought the presence of those feedback limiting diodes was a big
> part of the MS-20 filter sound. Maybe not as much on the cascaded OTA
> filter you're building, but certainly on the Sallen & Key Korg35 filter.

Yes, I think they play a much more important role in the Korg35-based
filter.  Tim Stinchcombe has written a 45-page paper on these filters:

http://www.timstinchcombe.co.uk/synth/MS20_study.pdf

>From his analysis it would appear that the diodes do very little in the
later filter, but are very important in the early filter.

I guess, based on my simulations, I don't even care that much whether my
filter sounds just like the original or not.  I think it will be a great
filter on its own merits.