[sdiy] ADSR sustain question

Tom Wiltshire tom at electricdruid.net
Wed Nov 20 13:26:10 CET 2013

On 20 Nov 2013, at 12:06, Colin f <colin at colinfraser.com> wrote:

> The sustain pot needs to be a low value otherwise as you move it nearer the
> centre position, it's own resistance will add to the effective value of the
> delay resistor, increasing the delay time.

This is the bit I don't get. The capacitor sees a Decay pot of value R with a voltage of X at the other end, and discharges towards X at a rate set by R. Why does twiddling the Sustain pot to alter X change this situation? And which bit of the Sustain pot is causing the problem? In centre I've got 5K toward Vdd, and 5K to ground. Which of these 5Ks alters the Decay setting and why doesn't the other one affect it too?

I've seen what actually happens. I was playing with an envelope on my bench this morning and I realised I just don't really get why, and that I ought to understand it better.


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