[sdiy] Prophet VS a phase accumulator design?

[Scott Nordlund]

> * Dave Smith said:
> * "Dont remember much of the details. I think we had custom chips
> * that shifted the sample rate, but not sure. The Evolvers use the
> * same waveshapes as the VS, otherwise it's different."
>
>The Evolver uses a ADSP-2191M for the oscillators and delays.

I think the Evolver is not a great implementation of this. The 
sample rate is too low (48 kHz?) to get away with the low resolution
wavetables and no multisamples, especially with all the FM and stuff.
It works for bass sounds and noise, and I understand it wasn't really
intended to be an all purpose high fidelity machine, but it's not an
ideal example to follow.

> An instrument who failed misserably using the DW8000 principles where
> the Kawai K3, serious octave miss match, one could clearly hear that a
> different table was used.

My Keytek CTS-2000 isn't so great in this department either.

I will say though that the early Casio Consonant-Vowel stuff is nearly
great. The waveforms are very low resolution (16 steps) and buzzy, but 
very bright and clean. The HT series has a uniquely excellent triangle
wave.

> Hmm, and then we have te mysterious DSS1 oscillator 18pieces of
> 8253 timers and a custom DMA chip.It seams that the band limitation
> software Chriss mentions are included into the DDS1 to directly
> compute the band limited octaves(waveform mode only or does it
> also do that on samples?) DSS1 schematics says variable sample rate
> would that suggest a timer rollover tick to do a DMA sample transfer
> but that sounds very slow and would limit replay range?!

I saw the DSS1 service manual recently. It seems to use a single 
multiplexed DAC, like the DW-8000. This would indicate a fixed sample
rate.