#3 Standard WoggleBug Circuit

The "WoggleBug" is a random voltage generator with application in voltage controlled electronic music synthesizers. It is a continuation of "smooth" and "stepped" fluctuating random voltage sources pioneered by Don Buchla. Additional research was done by Serge Tcherepnin, who coined the terms "smooth" and "stepped". The core of the circuit is based on the Buchla Model 265 "Source of Uncertainty" module. The design is expanded by using a CD4046 phase locked loop chip as a voltage buffer for Sallen-Key very low frequency smoothing filter. This adds a free linear VCO and ring modulator for your 40 cents. A novel method is used to get a 0-10 volt sawtooth out of the 4046. This is the source for the sample and hold, which makes the circuit "recursive" in some sense. The correlation control allows resampling of the S/H output and is another recursion level.

A new circuit, basically a phase locked loop which is tracking the "smooth" tone, is "kicked in the ass" every so often to cause the PLL to readjust the voltage for loop lock. The phase lock mechanism is a closed loop control system, and the lock voltage "rings" during readjustment, forming damped sinusoidal signals. At fast lock rates the ringing tones sound like plucked bass strings, at slow lock rates the voltages "woggle" and simulate string player vibrato.

Thanks to Don Buchla for inventing such a cool circuit, Dr. Mabuse for making RVGs so interesting, Bjorn Julin for the tip on the 4046 sawtooth output and Dan Slater for discussions of patching "lossy" FM telemetry systems, which lead to the "woggler" circuit.

An mp3 of two of the circuits feeding a mixer and Knight Kit spring reverb. WoggleBugDemo.mp3 (1.5M)


Block Diagram of 1/2 original Buchla Model 265 "Source of Uncertainty"

Block diagram of "smooth" and "stepped" WoggleBug core. The VCO sawtooth is the source for the sample and hold.

Block diagram of "Woggler" section. The circuit demonstrates a novel use of the VCO current programming input

Download Schematic Diagram of the #3 Standard WoggleBug (911K)