Erica Synths EDU DIY EG Eurorack Module Kit - Manual (Page 6)

ENVELOPE BASICS
If you’re new to modular synths (or even synths in general), you might ask: what’s an
envelope generator – and what do we use it for? Simple. We’ve only got two hands, best
case. So there’s a hard limit to how many of our synth’s knobs we can turn and
parameters we can tweak at the same time. Also, those hands are generally sluggish,
sloppy and imprecise.
Wouldn’t it be much better if we had some virtual, programmable robot hand to help us
out? That would do what we tell it to do, reliably and precisely, whenever we want it to? If
your answer is yes, then you might be a control freak. Also, you’d probably want an
envelope generator. So let’s build one!
But before we can do that, we have to understand what an envelope does, exactly. How
does it tweak parameters on another module?
Well, when designing oscillators, filters
and amplifiers, you’ll notice that people go to great lengths in order to make them
voltage controllable
. This comes in handy for us. Because if we want a filter module to
open up, for example, we can simply send a high level voltage into its CV (control voltage)
input. Now of course, if we only want to open the filter (and keep it open), we could send
in a fixed 12 V signal and be done with it. That’s not all that useful, though. Normally,
you’d want the filter to close at some point, too. So why not simply use a square wave
oscillator here?
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