[sdiy] Multiplying DACs

[Magnus Danielson]

On 28/01/11 11:48, Matthew Smith wrote:
> Hi Folks
>
> Sort of pursuing my wavetable idea, I was having a look at the
> spreadsheet that tells me what's in my various bits boxes and I
> discovered that I have a pair of MX[something] multiplying DACs.
>
> If I a) bumped my resolution up to 12 bit (which would tie in with my
> EEPROM-based concept) to suit these DACs, can I actually frequency
> modulate just by applying a signal to the external reference pin? Or
> would I be amplitude modulating?

That would be amplitude modulation.

Phase and frequency modulation you do prior to waveshaping for best 
result. For a phase-accumulator design you do frequency modulation by 
adding the modulation to the frequency input off the phase-accumulator, 
and you do phase modulation on the output of the phase-accumulator but 
prior the waveshaping.

Cheers,
Magnus