[sdiy] Buchla 257 is an extremely strange circuit

[Aaron Lanterman]

On Dec 16, 2009, at 2:50 AM, Derek Holzer wrote:

> my apologies of this thread is dead and buried, but I'm interested in analog computer functions and ways of "interpolating" or cross-fading between them, or between the input signal and the processed signal. This PWM AM sounds rather complicated to implement, would there be a simpler VCA-based solution? Something like the Serge sound processing module with it's voltage controlled cross fader? or am I missing something important in the concept of a CV crossfader/interpolator?

Yeah, the PWM AM approach is really complicated... Buchla puts a boatload of filtering on the output. ("Switched capacitor" filters work along the same lines.)

I imagine a VCA type solution would be easier in many respects.

My gut is that the PWM AM would be rather precise in the sense of DC offsets compared to VCAs... maybe.

- Aaron