Difference between revisions of "Envelope generator"

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[[File:ADSR parameter.svg|thumb|300px|The amplitude over time of an ADSR envelope. Only the positive half of the signal is shown.]] Sound synthesis techniques often employ an '''envelope generator''' that controls some parameters of a signal or control voltage at any point in its duration. When it controls a [[VCA]] these together form an '''envelope shaper'''.<ref>''Synthesizers for musicians'' by R A Penfold, PC Publishing, 1989, ISBN 18707750151-870775-01-5, p.21</ref>
 
== Timbre ==
ADSR envelope generators can be used for various functions. The most important use is to give timbre to a sound. Timbre is what makes one instrument sound distinct from another, even when playing the same note and at the same volume.
 
== ADSR ==
Most often the envelope generator is an ADSR (Attack Decay Sustain Release), which may be applied to overall [[amplitude]], [[frequency]], or [[filter]]. It is usually triggered by a [[gate]] signal from the keyboard.<ref name="q109">Synthesizers.com [http://www.synthesizers.com/q109.html Q109 Envelope Generator]</ref>
 
:The time taken for the level to decay from the sustain level to zero after the key is released.
 
A common variation of the ADSR on some synthesizers, such as the [[Korg MS-20]], was ADSHR (attack, decay, sustain, hold, release). By adding a "hold" parameter, the system allowed notes to be held at the sustain level for a fixed length of time before decaying. The [[General Instrument AY-3-8910]] IC included a hold time parameter only; the sustain level was not programmable. Another common variation in the same vein is the AHDSR (attack, hold, decay, sustain, release) envelope, in which the "hold" parameter controls how long the envelope stays at full volume before entering the decay phase.
 
Certain synthesizers also allow for a delay parameter before the attack. Modern synthesizers like the [[DSI Prophet 8]] have DADSR (delay, attack, decay, sustain, release) envelopes. The delay setting determines the length of silence between hitting a note and the attack.
 
== Usage ==
For shorter envelopes at higher [[pitch]], as happens in [[acoustic instruments]], a master [[CV]] is taken from the same voltage as used for [[VCO]] pitch.<ref>Description of the [http://www.cgs.synth.net/modules/cgs116_env.html Serge Extended ADSR Envelope Generator]</ref>
 
{{Lacks references}}
 
== Further reading ==
* ''The Complete Guide to Synthesizers'' by Devarahi, Prentice Hall, 1982, ISBN 01316063010-13-160630-1, pages 74-91
 
== External links ==
* [http://www.synthesizers.com/egpunch.html Q109 Envelope Generator Punch]
* [http://www.soundonsound.com/sos/jul99/articles/synthsecrets.htm Synth Secrets, Part 3: Modifiers & Controllers]
* [http://www.soundonsound.com/sos/nov99/articles/synthsecrets.htm Synth Secrets, Part 7: Envelopes, Gates & Triggers]
* [http://www.soundonsound.com/sos/dec99/articles/synthsecrets.htm Synth Secrets, Part 8: More About Envelopes]
* [http://173.201.189.104/forum/viewtopic.php?t=31473 What are all the ADSR's out there to build?] on electro-music.com
* Muff's Modules & More Forum:[http://www.muffwiggler.com/forum/viewtopic.php?t=83193 CEM3310 equivalent circuit]
=== Kits ===
* MFOS [http://www.musicfromouterspace.com/index.php?CATPARTNO=NONE&PROJARG=ADSR001%2FADSR001.html&MAINTAB=SYNTHDIY&VPW=1150&VPH=777 ADSR Envelope Generator]
* MFOS [http://www.musicfromouterspace.com/index.php?CATPARTNO=NONE&PROJARG=DUALARGENERATOR%2FDUALARGENERATOR.html&MAINTAB=SYNTHDIY&VPW=1150&VPH=777 Dual Attack Release Envelope Generator]
* [http://www.cgs.synth.net/modules/cgs116_env.html Serge Extended ADSR Envelope Generator]
* Oakley [http://www.oakleysound.com/vc-adsr.htm Voltage Controlled ADSR and VCA module]
* Oakley [http://www.oakleysound.com/adsr.htm Looping ADSR with integral VCA]
 
=== Schematics ===
'''Readily available analogue IC and discrete component based'''
* Formant music synthesizer by [[C. Chapman]], Elektor, 1978, p. 64, using [[Operational amplifier|op-ampamps]]s and common [[discrete]] components
* [http://yusynth.net/Modular/EN/ADSR/index.html yusynth ADSR] has a [[555]] core with a few op-amps.
'''CEM IC based'''
* Digisound 80 [http://www.digisound80.co.uk/digisound/modules/80-10/80-10.htm 80-10 Voltage Controlled Envelope Generator], uses [[CEM 3310]]. ''Electronic Music Circuits'' by [[Barry Klein]],1982, p. 62-3, includes [[Charles Blakey]]'s independent trigger input modification.
* Digisound 80 [http://www.digisound80.co.uk/digisound/modules/80-8/80-8.htm 80-8 Dual ADSR], uses CEM 3310
* Digisound 80 [http://www.digisound80.co.uk/digisound/modules/80-18/80-18.htm 80-18 Dual Multi-Function Envelope Generator], uses CEM 3310
 
[[Category:Synthesizer components]]