[sdiy] Digital Waveshape Generator.

[John]

On Fri, 11 Jul 2025 15:39:57 -0500
Phillip Harbison <alvitar at xavax.com> wrote:

> I guess the main question I have is does it make sense to have all
> this waveshape precision when a 44 kHz sample rate captures music
> with a level of fidelity I think most people find acceptable if not
> ideal.

If you feel it's worth doing, just for the sake of it, it's worth doing
;)

Wrt. the question of clock-divider accuracy and max. frequencies, the
other simple approach you could take is the "phase accumulator" - this
being an adder-based counter (rather than a simple incrementer) where
pitch control comes from changing the value added to the accumulator
each cycle.

This introduces a certain amount of jitter compared to the clock-
divider approach (where the possible frequencies might not be musically
"correct," but are *constant,*) but in practice this isn't a problem
(the error margin carries over to the next cycle and balances out over
time.) The SID chip in the Commodore 64 and Bob Yannes's subsequent
designs at Ensoniq used this approach.

(Absolute wavetable position could either be taken directly from the
top N bits of the accumulator - which is simple, but does mean samples
might be skipped - or from a separate counter clocked when the phase
accumulator overflows.)