digital control of analog component question...

[Martin Czech]

:::
:::	This opens up a whole new topic of discussion on how to interface
:::the D/A to the analogue circuit. I was grilled on a question about the
:::difference between VCO's and DCO's in an interview for my current
:::employer, and the only difference I could think of is that a DCO is a VCO
:::with D/A on all the CV inputs. Then it got me to thinking, how many

Well, I think this is not so easy.

If you work with fixed sampling frequency you will run into serious
interpolation problems. Even a simple square wave will be a headache
then. Look how long it took, until the industry came up with reasonable
dsp oscillator substitutes. Tune them higher, what do you hear: alias.

If you opt for variable sampling frequency you end up with very high clock
frequencys that have to be as precise as any other vco, nevertheless.

So, building a reasonable dco with smooth glide, no alias, no zipper,
and precise frquency is quite demanding.

m.c.