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Eurorack exponential ADSR envelope generator with range switch (4HP - PCB/panel)
York Modular

Eurorack exponential ADSR envelope generator with range switch (4HP - PCB/panel)

2 in stock.

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An updated version of the old 5HP ADSR module - functionally the same as its predecessor, albeit with a couple of changes. First, the range switch is now fitted to the mainboard itself rather than the front of the module, and second there's now an LED. It fits inside 4HP too ... so that's three things.

This is an updated envelope generator which uses a 555 timer configured as a Schmitt trigger (see: - figure 15 in particular) from which the envelope is generated. The net result is something that not only triggers at around 1V but also has far fewer parts.

I'm going to call that a win, and it isn't dissimilar to the design that Doepfer use in their EG modules, albeit without the bells and whistles.

In addition, I've 'borrowed' a couple of features from a Rene Schmitz design, specifically: the resistor R13 is optional, but adding it will give the input a bit of hysteresis (the degree of which is governed by the values of R13 - 1MΩ is what I use) which is handy if you're using a slowly changing waveform as a trigger.

Secondly, there's a buffer between the sustain and decay pots which removes any interdependence between the two. It also uses up an otherwise uncommitted op-amp. There's a range switch on the mainboard too - envelope values are governed by the control pots and the values of the two capacitors.

THIS IS A PCB/PANEL SET - a suitable switch, right-angle power header and power cable are provided but it is up to you to provide everything else and put it together. The three SMD transistors have been pre-soldered for you.

You can get the BOM and schematic at:


CURRENT DRAW (approx.):

  • 20mA (+12)
  • 5mA (-12)