2 x one-shot/cyclic event generators based on CMOS envelopes used in EDP Wasp and Gnat
Chris Huggett, chief designer at EDP came up with a novel little circuit for the filter envelope of the Wasp, based around half a CD4013, half a CD4066 and half a LM3900. It was an A/R generator with looping option which would proceed through its whole cycle from only a trigger input. He further developed the circuit for the filter envelope in the Gnat to use just one knob to provide a range of attack envelopes when anti-clockwise (from 12 o’clock), and a range of release envelopes when clockwise (from 12 o’clock). 12 o’clock gives a very short symmetrical blip. As you can build two of these with a CD4013, CD4066 and LM3900, we’ve provide both a two knob version and a one knob version, each has it’s own place.
We have re-engineered these ideas for Eurorack, and added a couple of useful features:
As both circuits are based around flip-flop, we’ve provided Q outputs and not-Q binary outputs (ie. either low or high). Q describes the attack cycle, whereas not-Q describes the release cycle on both envelopes. There are numerous applications for these outputs.
The Gnat A/R did not have a looping function – we’ve added that as it’s a useful extra.
We’ve included a Go! Button, which manually actuates both envelopes.
The second envelope’s gate input is normalised from the first envelope’s gate input. This can be broken by patching a jack to the second envelope’s gate input.
