[sdiy] Hybrid (analog/digital) vocoder?

[Paul Perry]

Just saw mention in the CMOS switch as VCA thread that some famous
vocoders use PWM for the VCA.
So I thought - not to complicate matters - to start a new thread, on the
question of  a 'hybrid' vocoder, in which the  filters are analog, but the
VCAs are digital, and the PWM is controlled by DSP.
The idea is, the carrier remains analog throughout, with a PWM VCA.
But the analysing is done in a DSP or micro, digital outputs from which
control the various filters in a PWM fashion.

This would have the advantage that
1. the filters are all analog, giving possiblility of resonance knobs on 
each.
2, the PWM - which can be tricky - can do the difficult parts - no
comparators needed - plus the analysing filtering can be in software
without affecting 'musical' quality.

paul perry Melb Aust