tri 2 saw modualtion

[Joachim Verghese]

> Do you know how to analyze a PWM sweep?

The harmonic structure of any rectangular waveform can be described
with the [sin x]/x (a.k.a. "sinc") function, where x is proprtional to
frequency (harmonic number) and mark/space ratio. Nulls appear where
[sin x] equals zero.

If you modulate the m/s ratio (pulse width) you'll end up with an
expression that contains sin(sin y), which is not unlike FM/PM at
all, hence the utilisation of Bessel functions. Well, this is about
as far as I've got with the maths at this point...perhaps other
list members can fill in here.

> Another for the synth list: the Matrix-N family has saw/tri modulation
> on the audio oscs.  I've never looked at the waveform, though.

Actually, the Matrixes (Matrices?) that have real VCOs do not have
any saw/tri mod, if memory serves. The DCO-based ones (M-6, M-1000)
do have, but it's just one of those pulse/tri/saw combination
tricks that goes on in the CEM3396. Check the 3396 data sheet at

http://www.synthtech.com/cem/cemdata.html

-joachim