Erica Synths EDU DIY EG Eurorack Module Kit - Manual (Page 9)

PASSIVE A/R ENVELOPE
So how can we separate the two? It’s actually really easy. All we need are two diodes and
another 1M potentiometer.
Here’s how this works. Diodes are basically one-way streets for electricity . So by 7
putting two of them in parallel, facing in opposite directions, we are taking a two-
way street and splitting it into two one-way streets
. Where before, our capacitor was
charged and discharged through the same resistor, now each phase gets their own.
So when the input signal swings high, a current will flow through the top diode – and only
that diode – through the top potentiometer and into the capacitor. During the low phase,
the current will take the other path. This means that one potentiometer now controls the
attack – and the other controls the release.
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If you connect your LFO and VCF like before, you should be able to sculpt the filter
movement much more freely by adjusting attack and release independently. So what
we’ve built here is an ultra-simple passive attack-release envelope generator. Why
passive?
Because it does not include any form of amplification . It’s getting all of its
Read more about diodes in the components & concepts appendix (page 28). 7
You can try this chapter’s circuits in a circuit simulator. I’ve already set them up for you right 8
here: https://tinyurl.com/y7xguhoo – you can change all values by double clicking on
components.
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