[sdiy] How DCOs work

[Andrew Simper]

On 12 October 2016 at 09:24, David G Dixon <dixon at mail.ubc.ca> wrote:
>
> It seems to me (and, bear in mind that I know nothing about DCOs) that one could use a standard VCO circuit to control the current to an integrator, and use a digital circuit for the reset.  In this way, the only "tracking error" would be a slight loss of amplitude at high frequencies, and FM would still distort the slope.
>
> What am I missing?
>

You could actually use this to generate some cool "sync" type sounds
with a "single" oscillator, apply a voltage to the pitch of the VCO
for FM and then it will re-sync at the correct pitch :)

Otherwise, if you are outputting the control current (or voltage that
gets converted to the control current) digitally then you would need
to have a digital accumulator to get the FM re-sync in roughly the
right position. If you're already doing this with an ADC with enough
resolution I would ask why bother with the VCO, you could just output
the sawtooth waveform directly!

Andy