[sdiy] Buchla 257 is an extremely strange circuit

[Paul Perry]

I think you could get better results with PWM at lower frequencies - but
with PWM, there is the problem of aliasing artifacts, just like sampling.
So you need filtering both before & after the PWM, ideally.

On the other hand, with OTAs, there is the noise level. But, the OTA will go
perfectly well even up into MHz with no problems.

I must say, whenever I read the history of the Wavemaker partners, it's hard
not to cry.
Makes one wonder how many other synths there were, that didn't even get as
far as theirs.
>From the documents, their derivation from contemporary analog computers is
even more apparent than usual. PWM was a standard technique for
multiplication in the old analog synths - the width is one variable, the
amplitude of the chopped signal is the other. So you have "two quadrant"
multiplication pretty easily.

Paul perry Melbourne Australia

-----Original Message-----
However, actual units I have examined use 
more conventional OTA based filters.  It is possible that Terry Kincaid 
did initial versions with the PWM method, then moved to OTA versions, 
probably due to superior audio quality.

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