[sdiy] BLIT/BLEP virtual analogue synthesis

[Olivier Gillet]

What I had in mind was more a traditional setup with 8 voices, 3 or 4
oscillators per voice, sort of like the Ensoniq DOC...

> On the other hand, if your goals are to have just a few oscillators then
> it's fairly trivial to run them at a very high sample rate and use
> bandlimited decimation to get them down to rates that a common audio DAC can
> accomodate. I've got some prototype designs that generate a small number of
> simple sawtooths at around 1MHz, sum them together and downsample to 48kHz
> which sound quite good. Rough estimate at these rates suggest that for a
> 1kHz saw the in-band aliases will be about 60dB down - not too bad in
> comparison to the spectra in Antti's IEEE paper.

Would it be a stupid idea to get away with the downsampling, put
instead a sigma-delta loop and just output a bit at, say, 8 Mhz, so we
could also get away with the DAC and just put a simple analog low-pass
on this bitstream? Am I wrong to suspect that the very first thing a
modern audio DAC would do with the signal you have carefully
downsampled to 48 kHz, is to upsample it back to several MHz for
sigma-delta conversion?