[sdiy] New dsPIC chips with on-chip audio DACs

[Eric Brombaugh]

jbv wrote:
> as I love to play the devil's advocate once in while, I'd like to ask if
> 
> building synth voices is really the only horizon that offer those new
> & cheap & fast dsPIC chips ?
> I really don't want to trigger any flame war, but I just wonder if it's
> sufficient (if not a bit frustrating) to approach these chips only from
> an analog synthesis point of view (MIDI -> DCO -> VCF -> VCA)...
> 
> I'm no dsp wizard, but well, a little bit of imagination never kills...
> so why not ask how many osc can be run in parallel for additive
> synthesis, if FFT/iFFT or NN or GA can be implemented, and how
> it could paved the way for new kinds of music gear (affordable and
> made by DIYers), and why not for new kinds of music ?

Of course you can try a fully digital signal path. The difficulty you'll 
run into is that the dsPIC internal data buses are only 16 bits wide, so 
there's not enough dynamic range in the processing to do really high 
quality audio DSP.

While 14 to 16 bits is sufficient for an oscillator that's always 
running near 0dBfs, as soon as you try doing filtering and VCA functions 
internally you'll find that noise lurking underneath it all. Doing those 
functions externally in analogue eliminates that issue.

OTOH, if you don't mind the noise or are willing to take the performance 
hit of cooking up some high-res math operations by combining the 16-bit 
instructions then you absolutely can do what you've suggested. The dsPIC 
supports bit-reversed addressing for doing FFTs, and relatively 
efficient implementations of both FIR and IIR filtering are possible.

Eric