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ADSR Envelope Generator

ADSR ADSR

An envelope generator modeled on the 555-based ADSR originally proposed by Jonathan Jacky. It's worth looking through the evolution of this design - see references below.

  • Module size: 6HP (30mm)
  • Power: 10mA (+12V); 9mA (-12V)

Project Source

The project files, including schematic and layout, are available on github.

Features

  • ADSR controls
  • Gate input: control signal, button or loop input
    • Schmitt-trigger buffer for control signals and button
    • Independent rate control for the loop (equivalent to sustain)
  • Trigger (rising edge) input: initiate an A/D or A/R cycle
  • Loop mode with adjustable sustain period (LFO behaviour if desired)

When a gate signal is removed, the release phase of the cycle will start immediately (independent of the envelope level). When a trigger input is applied, the envelope will always go to its maximum level before transitioning to the decay (gate signal still applied) or release phase (gate signal absent). See the Design section for more details.

Documentation

References

  1. Jonathan Jacky, "Two-chip generator shapes synthesizer's sounds", Electronics #11, September 1980 : 137-138 archived on yusynth.net
  2. Rene Schmitz, "The Fastest Envelope in the West", online schmitzbits.de (ca. 2000)
  3. Yves Usson, "Envelope generator ADSR (newer version)", online yusynth.net (2010)
  4. Kassutronics, "Precision ADSR", online kassu2000.blogspot.com (2015)
  5. Moritz Klein, "mki x es.edu Envelope", Erica Synths, online ericasynths.lv (2021)
  6. Eddy Bergman, "Synthesizer Build part-63", online eddybergman.com (2024)