[sdiy] Linear vs. Exponential control of VCA's

[Scott Bernardi]

The decay and release curves are decaying exponentials (i.e., exponential
approach to zero) while the attack is an exponential that approaches a
non-zero value. Both are "natural" responses. Musical instruments that are
percussive in nature (struck or plucked strings, drums) will have a decaying
exponential amplitude envelope.  If you think of it, the response of an RC
filter to a step function is a natural one too, and that's basically what an
envelope generator is (AR).
I'm thinking a linear ramp generator driving an exponential VCA is the same as
an exponential EG driving a linear VCA.
I guess my question is, what are people using in their systems? What do some
of the old classic systems (Moog, ARP, OB, etc.) use? Has anybody ever done
any comparisons?

jorgen.bergfors at idg.se wrote:

> >VCA's are usually controlled by envelope generators which already
> >output exponential waveforms, so if you input these into an exponential
> >control input, aren't you getting a "double" exponential response?
>
> Not really. The output curve of a typical envelope generator is
> exponential, that's true.
> But the exponential curve is "upside down" in the decay and release phase.
> I suppose the best thing would be a linear envelope generator and
> exponential VCAs. Or isn't it?
>
> /Jorgen

--
Scott Bernardi
sbernardi at home.net