[sdiy] Prophet VS a phase accumulator design?

[Paul Maddox]

> I think almost every sane (i.e. not Fairlight/Synclavier)
> polyphonic implementation is fixed rate, just some are
> high frequency.

And this is where people struggle.
The "addition" i.e. the Phase Accumulation part is a fixed rate, the
resultant output, isn't.

So it's really hard to say if it's fixed rate or variable rate... it
depends on what rate you're talking about.

using a phase accumulator the output wave (i.e. DAC) is only updated
on a change, the change may occur slowly, or very quickly. with a
traditional DSP based system the output waveform (i.e. DAC) is updated
at a constant rate.

> Where I'm less clear is the Emulator/Emax stuff. Older
> variable rate samplers like the Fairlight required a
> separate sample RAM per voice, but the Emulator
> apparently kept the fixed sample rate, using a single
> shared bank of RAM and apparently some sort of DMA and
> small RAM buffer per voice.

Terry one for you?

My guess would be they're using a phase accumulator, just the like PPG
does to play back samples (remember the wave 2.2 and 2.3 could
playback samples recorded using the Waveterm).

Paul