ADSR Envelope Generator

Attack-Decay-Sustain-Release envelope generator, an expansion on Ray Wilson’s Music From Outer Space design.

This module is used to generate a contour control voltage in a synthesiser. It’s what helps make a sound snappy, or makes it smoothly fade in and out. It can be used in combination with a lot of components, but that is the general idea.

I wrote an extensive write-up about the original circuit and my additions to it, fully detailing how the whole thing works; this can be found over on synth.michd.me.

The circuit design is based on Ray Wilson’s ADSR design, with these additions:

  • LEDs in the sliding potentiometers indicate which stage the generator is in
  • Option to retrigger itself when the decay stage ends, which essentially turns it into an oscillator
  • End-of-decay trigger output
  • Additional timing range

The panel contains two of the boards on the back, as seen here:

Work Involved

  • Additional circuit design / prototyping on breadboard
  • Schematic capture (KiCad)
  • Circuit board design (my first one involving surface mount technology) (KiCad)
  • Front panel design (Inkscape)
  • Laser cutting, on local makerspace’s laser cutter
  • PCB assembly (reflow oven, and through-hole soldering)
  • Panel assembly

You can view the full schematic (PDF) , and browse all the design files on GitHub.