[sdiy] favorite adsr?

Antti Huovilainen ajhuovil at cc.hut.fi
Fri May 29 16:03:39 CEST 2009


On Fri, 29 May 2009, Dave Kendall wrote:

> If expression is your thing, I'd recommend a VC ADSR. There is a nice

VC ADSR is easy to do once you realize that ADSR envelope is just a 
lowpass filter with three switched "cutoff frequencies" (time constants 
really).

For attack phase the input is set to 1.5x envelope peak voltage 
(technically 1/(1-exp(-1) = 1.58, but the difference is tiny). For decay 
it's connected to sustain voltage and for release to ground.

Typically you want the times to be scaled by 2^octave, so a normal expo 
converter works great.

LM13700, two comparators and a bit of logic and you get dual VC ADSR.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova



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