envelopes.md

+# Envelopes
+An Envelope Generator is a circuit that generally produces a rising voltage followed by a falling voltage, adjustable over time.     
+It is most often used as control voltage for a [VCA](https://code.hfbk.net/sdiy/documentation/wikis/VCA).    
+The various voltages involved are called stages, and there are various different envelopes with a different amount of stages.    
+The simplest envelope is an AD (Attack-Decay) or AR (Attack-Release) envelope with only two stages: One rising and one falling voltage.    
+AR.jpg    
+[Niklas Ronnberg AR envelope](http://familjenronnberg.se/~niklas/diy/eurorack/ar/)    
+A slightly more complex form is the ADSR that has four stages consisting of Attack, Decay, Sustain and Release.    
+ADSR.jpg    
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