[sdiy] ADSR Sustain pot law?

[Neil Johnson]

All,

While putting together a list of replacement pots for my "Jenny" project,
I was looking at the envelope generators and noticed that the two sustain
pots are both linear.  Now, since in this synth everything is hardwired
(rather than patchable) it strikes me that it would make better sense to
replace them with log-law pots, which would lead to a more natural
behaviour:

- VCA: sustain sets steady-state volume, so log-law would lead to natural
"linear" setting (same as volume control);

- VCF: sustain sets steady-state cutoff frequency: this is linear w.r.t.
the control voltage, so for a "musical" control reponse would need a
log-law curve, producing a 1-2-5-10-20-50-100, not 1-2-3-4-5-6-7,
behaviour, so that the same rotation angle produces the same octave shift
irrespective of where on the scale you are.

I think in general, for a fully patchable modular system, a linear sustain
control makes sense so that, for example, controlling a pitch envelope
would produce the right behaviour (comment: unless the CV input of the VCF
or VCA is exponential, then the linear sustain control curve is now
wrong!)

Anyway, I'mm going to try out log-law pots for both sustain controls and
see how it feels.

Does this make any sense, or am I barking up a tree again?  *woof*

Cheers,
Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
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