Frisson

natural complex chaos based on Mackey-Glass equations

This is a chaos module based on the Mackey-Glass equations which were developed to show the delay in physiological systems when producing or reducing certain cells in response to variations in concentration of those cells. The result is a very complex and easily controllable chaotic pattern.

The basic Mackey-Glass system implemented into electronics is a nonlinear stage, a low pass stage and a delay stage connected in a loop.

In this circuit the delay stage is made of 8 Bessel filters, configured for sub-audio rates, which are voltage controlled via LDRs, this section is very similar to an 8 stage phase shifter. Each filter stage has an output to the front panel. There is also an external input to inject signals into the chaos which is rather interesting.

Controlling the Delay section with CV, or via the knob, sets the frequency of the chaos. The chaos knob changes the pattern. The module self-oscillates, so can run happily with no inputs. It may pause for a while if the Chaos knob is turned to maximum, but runs at other settings. When CV or other signals are injected it runs at all settings.

If the switch is flicked to CV Phaser, then the Bessel filter section can be used, along with the feedback pot, as a voltage controlled CV Phaser, with 8 differing outputs of slightly delayed and increasingly slewed versions on the original CV can be obtained.

The feedback pot only works in CV Phase mode, it is switched out of the circuit in Chaos mode.

The module can be built to operate at different frequency ranges, capacitor values are given in the Build Notes. I prefer the slowest version, but feel free to go your own way, or build all 3. You can try other values if you want to. Generally C2 should be approx. double the value of C1 and C3/4 (these are in parallel so add together) should be 10-20x greater than C2

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