[sdiy] Digital Waveshape Generator.

[Donald Tillman]

On Jul 11, 2025, at 4:30 PM, rburnett at richieburnett.co.uk wrote:

> 
>> I don't see any advantages to a divider approach.  And there are a
>> number of disadvantages, such as the lack of portamento that you
>> mentioned in your writeup.
> 
> The advantage of this divider approach is that you don't get any aliasing because each pitch period is an integer number of samples at whatever (variable) sample rate the wavetable is currently being played out at.
> 
> This isn't the case for phase-accumulator / DDS based designs with a fixed sample rate, where you either have to have lots of copies of the waveform in memory with progressively fewer harmonics for the higher notes to eliminate aliasing _OR_ instead choose a *very* high sample rate and settle for whatever aliasing remains.

I believe it's standard operating procedure to store waveforms that won't alias at the intended frequencies.  And that this usually involves separate waveforms for each octave above a certain point.  And that's not really a problem because for each octave up you only need half as waveform many entries.

Not that I'm endorsing digital oscillators or anything...

  -- Don
--
Donald Tillman, Palo Alto, California
https://till.com