Fri Jan 7 19:54:06 EST 2011
More hands-on verification pending, it seems that the VCO part is
solved, and if the temperature control works, digital VCO control
and VCA should work too.
The remaining question is then how to implement envelopes. These
should probably be analog. As opposed to the VCO,VCF,VCA trio which
ironically are all current-controlled, the envelopes might work best
with voltage controlled resistors, i.e. FETs.
The main reason is that exponential attack/decay just sounds really
good, especially in the low time constant range. Frankly I don't want
to mess with that trying to fake sharp transients digitally. It would
probably take significant effort too.
So how about the FETs then? I suppose this is an area where the
CD4049UBE might shine, as all we need to do is charge / discharge
capacitors at a variable rate. The rate resolution is probably not
even critical, as long as it is +- logarithmic.