Snake Joke

Euclidian pattern & Cv generator by Tom Hirst

The core of this module, where the logic and processing happens, was designed by Tom Hirst. Tom has been using the design for a few years in his 4U system and got in touch with me to release it as a Eurorack version. I was quite impressed that he had refined the circuit down to just three CMOS chips, built one and liked it.

So here we are:

The circuit is a CMOS based Euclidian trigger, gate and CV generator. You can use the switches (or input signals to over-ride the switches) to select how many triggers will be delivered per 16 steps. The circuit will “do its best” to evenly space the triggers over the 16 steps.

It is interesting to patch in gates of the divided down clock signal (or anything) to switch between patterns on the fly. Sometimes the patterns can go a bit awry, when switching mid cycle, and you may want give the momentary reset switch a tickle, then again the awry patterns are usually good too so just go with it and things may return to normal eventually.

The C1-4 gate outputs are taken from the internal switching of the circuit. Hit gate and hit trigger are the main outs, but in practise they are all interesting.

CV is a simple D to A resistor network taken from C1-4. It covers an approximate 0-5V range, feel free to adjust the resistors here reduce or increase this.

Perhaps a limitation of this module, compared to other Euclidian pattern generator running microprocessors, it is fixed to 16 step patterns. Using the reset input and careful switch set up can get around this limitation. Also, being able to change the patterns on the fly makes this a very powerful and complex pattern generator.

https://www.nonlinearcircuits.com/modules/p/snakejoke