EG design

[Grant Richter]

> 
> Is there any point charging an envelope generators timing cap with a
> constant current source, variable of course, to generate a linear change
in
> output pd. Or do exponential rises and falls sound more realistic. mmm,
> there's a thing, realism, I'm not sure thats the right word. My D-50
(shock
> horror) seems to have linear EGs, at least the diagrams on the front
> suggest that, and they sound very odd on a slow attack/decay setting.
> 
> Any one built a analogue linear EG?
> 
The Buchla and Serge EGs are all linear slopes, as is the Wiard. The
thinking goes like this:

If you have a linear VCA then you need an exponential envelope to get it to
sound right. This is what Moog did. But the problem is if you want to use
the envelope for something else. Take panning for instance - you don't want
an exponential pan envelope, you want a linear one. Buchla and Serges
response was to use a linear envelope and make the VCAs exponential. That
way, the envelopes are more generally useful in controlling any parameter.

To summarize:
Linear VCA - Exponential envelope
Exponential VCA - Linear envelope