[sdiy] Ridiculously PC (Phase Correct)

[Grant Richter]

> 
> Or for LFO control signals, the 0-volt starting points of the various
> waveforms occur simultaneously, so that panning, switching or mixing
> the outputs does not change the effective rhythm of the LFO modulation
> or change the timing the 0-volt starting point.
> 

FWIW, a descending sawtooth used to feed a comparator, can be pulse width
modulated without rhythmic shifts when used as a clock source for a
sequencer (what Bernie Hutchins called "fixed edge PWM"). The back edge
changes the gate time, but the front edge is rhythmically correct.

Tightly phased waveforms are easiest in software (IMHO).

A wavetable playback device, such as a Mini-Wave, has all the fundimentals
time aligned. For example, two Mini-Waves driven by the same ascending
sawtooth will have close phase alignment (+/- 1.4 degrees).

A counter driven wavetable system will have phase alignment. Multiple
simultaneous waveforms could be demultiplexed from a single EPROM (scan out
4 waveforms at 4X the clock speed). There are problems with making an RF
oscillator track exponentially.

A reset VCO will have the square and sawtooth aligned but the triangle will
be in quadrature.

A reversing VCO will have square and triangle in quadrature also.