Envelope gen operation

[Steve Ridley]

There seem to be two approaches to this:

1. Simple designs go through the ADS part of the envelope
    until the gate stops, then go into the release stage.   If you
    apply a trigger pulse, the behaviour of envelope depends on
    the ADSR settings plus the gate duration.  With a long attack
    and short trigger nothing much will happen - the attack hardly
    gets started before release sets in.  With a longer gate pulse
    and relatively fast A and D times, you might get a very short
    but complete ADSR cycle.  These types are quite expressive
    when controlled by a keyboard gate, but not so good off
    trigger.

2.  Some designs won't go into decay until the attack phase has
     finished.  I would expect these to go through the full ADR cycle
     with no sustain time.  These are more useful for triggered
     sounds (percussion etc) but very frustrating when played from
     a keyboard - especially if you hit a wrong note.  The Moog Rogue
     does this...

You should take a look at the Digisound 80-18 envelope generator
schematics - I think they're up on Ander' website. This ADSR had
a choice of triggering modes so it could be used usefully with gates
or triggers (or both).   You can't get the CEM3310s any more, but it's
a source of good ideas.


Steve Ridley






-----Original Message-----
From: Tim Ressel <Tim_R1 at verifone.com>
To: synth-diy at node12b53.a2000.nl <synth-diy at node12b53.a2000.nl>
Date: 26 May 2000 23:42
Subject: Envelope gen operation


>Yo, list,
>
>I have a question on ADSR operation: If you get a trigger event without a
gate
>event, how do you expect the ADSR to respond? Does it do a full AR cycle?
Does
>it do nothing? Does it do a truncated AR cycle the width of the trigger
pulse??
>
>
>
>Tim Ressel--Compliance Engineer
>Hewlett-Packard
>Verifone Division
>916-630-2541
>tim_r1 at verifone.com
>
>