Möbius PiLL

A chaotic noise module after papers on mutually coupled PLLs (Shirahama et al.): two PLL chips whose phase detectors each go through a Buchla-style vactrol low pass gate, then into their own VCO and, inverted, into the other's. The PLLs share FREQ and its CV; each filter has its own. It runs on its own; a signal at IN makes it try to track it. The vactrols are built from LDRs and LEDs in a light-proof box on the PCB.

Key features

• IN, FREQ CV, LPG1 CV and LPG2 CV in
• VCO1 and VCO2 out (the PLL VCOs' pulses), LPG1 and LPG2 out (the filters)
• FREQ, LPG1 and LPG2 knobs, with FREQ CV, LPG1 CV and LPG2 CV attenuators
• 10 HP; Nonlinearcircuits publishes no current draw, depth or assembled price (it sells the DIY PCB and panel), and ModularGrid lists none