[sdiy] Buchla 295 10-band comb filter topology

[Donald Tillman]

> On Nov 22, 2022, at 2:01 AM, Lanterman, Aaron D via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> Does anyone recognize the topology Don is using here in the bandpass sections?
> http://fluxmonkey.com/historicBuchla/buchlaFiles/Buchla_2950_200.jpg <http://fluxmonkey.com/historicBuchla/buchlaFiles/Buchla_2950_200.jpg>
> 
> The low and high bands are 3-pole Sallen-Keys, but I’m not sure what’s going on in the middle filters.


Hey Aaron,

It's a twin-tee filter, but connected in an unusual way.  

The input is directed into the twin-tee's "ground", and the twin-tee's normal notch filtering action is the opamp's feedback loop.

  -- Don
--
Donald Tillman, Palo Alto, California
https://www.till.com
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