Phaseshift / Osc Sync idea

[Michael B. Irwin]

There is an interesting circuit called a "multiphase waveform animator
(algebraic sawtooth shifter)" described in the paper "Analog Circuits
for Sound Animation" by B. Hutchins. This appeared in the Journal of the
Audio Engineering Society Vol.29, No.11, November 1981. I do not know if
it was mentioned in Electronotes. The method involves comparing a  input
sawtooth to a reference voltage with a comparator, adding the comparator
output to the inverted input sawtooth, and re-centering the resulting
shifted sawtooth about ground. As many shifted sawtooths as required can
be derived from the input sawtooth by this method. I built a 4-phase
version of this 9 years ago, and the resulting sound is much richer (in
my opinion) than a 4-phase PWM signal. If it is intended  that the
multiplicity of shifted sawtooths be mixed together on one line (no
further waveshaping-similar to "Supersaw" on Korg AN1X) the circuit
becomes quite simple. The 4-phase control LFO was a quadrature sin-cos
oscillator with 2 additional phases derived by inversion, with
amplitude control of each output using OTA's. Regarding the master-slave
sync'd integrator idea the slave integrator must be reset by a
monostable connected to the comparator output which monitors the level
of the master sawtooth-else you won't get a 2nd sawtooth.