[sdiy] MS 20 FILTER

[Aaron Lanterman]

On Sun, 18 Dec 2005, harrybissell wrote:

>> MS10/20; one of these OTA-based 'clones' (which, to my mind, are not
>> Sallen-Key filters); and (if I can do it!) an OTA-based version which *is*
>> Sallen-Key, but which also has the Korg quirks, like the asymmetric

I'd be very interested in your results on that. I took a Sallen-Key, 
replaced the resistors with OTAs, and then couldn't quite make that match 
up with the schematic... in particular, to do a one-for-one replacement of 
the transistor that hooks to the voltage buffer/amp, you'd need two OTAs 
in parallel facing opposite directions, which isn't what's happening there 
- the equivalent resistor winds up working "one way" and you get a 
different transfer function.

- Aaron

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