[sdiy] ADSR sustain question

Tom Wiltshire tom at electricdruid.net
Wed Nov 20 12:54:00 CET 2013

Hi All,

There's something I don't understand about this envelope generator:


The Attack, Decay, and Release pots are all 2M2. Ok, fine. The Sustain pot is 10K. Now, I suspect this value is so low so as to avoid any interaction between it and the Decay pot, but I don't understand why this is the case - it's just my gut feeling, and one shouldn't think with one's guts. The brain generally does a much better job.
I understand that the Sustain pot acts as a potential divider and provides a voltage level below which the cap cannot discharge (the sustain level). But a potential divider could have *any* value - we could use a 10M pot if we could find one, and it'd still act as a potential divider. But as I said, I suspect that wouldn't work.

Can someone explain the choice of Sustain pot value in this circuit, and how/if it interacts with the Decay pot?


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