[sdiy] Details of the basic additive/FM voice Synclavier oscillators?

[Scott Nordlund]

> On 2/2/2011 11:44 PM, lanterma at ece.gatech.edu wrote:
> > While we're talking about Prophet VSs and Korg 8000s and PPGs and such, I was wondering if anyone had run across a clear description of the Synclavier guts. I'd love to see the actual circuits.
> >
> > I have the various Synclavier patents printed out, but they're a tough slog since they're written, well, like patents, which are not particularly noted for their clarity. ;)
> >
> See http://www.500sound.com/SyncII/synthschem.jpg
>
> http://www.500sound.com/SyncII/sync2intro.htm
>
> this is about the best description I know of on the web.
>
> Dale

There's a real shortage of good documentation, but I've looked into it a bit. That diagram should be pretty descriptive. You'll notice that it's variable sample rate and uses a hardware multiplier for modulator scaling. The carrier waveform is user definable, 24 harmonics. The end result is horrendously inefficient (separate expensive hardware for each voice) but doesn't suffer from aliasing or quantization noise due to amplitude scaling, or even loss of envelope resolution at low voice amplitudes. As far as I can tell, the design dates back to the Dartmouth Digital Synthesizer (circa 1974). So although Yamaha's eventual optimizations were far more advanced (the DX7 did it all one one ASIC with a log-sine ROM, exponential ROM, accumulator and 96 stage shift register), the Synclavier is a descendant of one of the first hardware implementations of FM.

I've heard people wishing for a software emulation, but I think it would require a great deal of oversampling to make it sound not terrible. And I don't think FM of additive/arbitrary waveforms is particularly impressive anyway, despite the Synclavier's "vintage halo". The good results came from clever software (timbre frames/resynthesis) and careful sound design (stacking tons of voices to make a sound).

And I don't really recommend it, but there's a bunch of old Jon Appleton stuff that rather unflatteringly depicts the Synclavier's "raw sound".