[sdiy] Prophet VS a phase accumulator design?

[Scott Nordlund]

> I believe you are thinking of the Emax II, which used Emu's G-chip to transpose over a 10 octave
> range (+/-5 octaves). The G chip had a fixed output sampling rate and allowed 32 channels of
> sample playback. It was also used in the Emu proteus line and EIIIX but I believe later samplers
> had an improved version. Assuming the G-chip matched with the Emu patent on its technology, it
> used 32 times oversampling with a polyphase FIR and then linear interpolation on the oversampled
> signal to fill the gaps. Upward transposition was not as alias and distortion free as the advertising
> claimed but still an improvement over many other samplers of the day.

I'd seen that patent, seemed far ahead of most interpolation algorithms at the time.

> The earlier Emax used the E-chip to perform add/drop sample transposition at a fixed rate around
> 1MHz, but bespite this had only very limited upward transposition. At the 41.6k sampling rate it
> could only shift up a few semitones but could transpose down a long way. Because of the output
> rate exceeded the sampling rate by 20 times or more, the result was more similar to using a
> variable sampling rate but with considerable sideband distortion at non integer intervals. Given that
> the samples were compressed down to 8 bit it probably was not so noticeable anyway.

That's a little disappointing, oh well.