[sdiy] Prophet VS a phase accumulator design?

[karl dalen]

--- Den tors 2011-02-03 skrev Scott Nordlund <gsn10 at hotmail.com>:

> 
> Well, the delays aren't interpolated either. At least it's
> consistent.

But! 160Mhz DSP?! 32bit clean Phase acc yes.

> > > 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.
> >
> > Didnt the casios use the Ralph osc design, 600khz
> sample rate
> > a 1 for up a zero for down? 1111100000=triangle?
> 
> I dunno what's going on in those ASICs, aside from the DPCM
> waveform
> storage thing, but it's pretty impressive. 8 voice
> polyphonic purely
> digital synthesis circa 1980. 
> It's not like it can be directly 
> compared to the PPG, but it 
> certainly seems more "engineered".

Check out a thread some months earlier there are a link to a
interesting paper, a study on the Hamamatsu area, the Casio
kawai digital osc are described in there with pat no and all. 

> > > 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.
> >
> > Absolutely sure on that?
> > Schemo/Manual says variable.
> 
> A true variable sample rate has to have a DAC for each
> oscillator. If it uses a single DAC, it's sequentially'
>outputting each one. It can't  do this asynchronously.
>So it's got to be, I guess, a time
>shared fixed rate phase accumulator type thing.

? So the ESQ1 are fixed and the PV-S the same then?
I tought we hade come to the conclushion a phase acc
would be seen as variable sample rate despite the fixed
rate computation? No?

Ahh, had no idea the PPG was fixed rate osc. ;)