[sdiy] VCO tuning philosophy re-visited

[David G. Dixon]

> I can see the attraction of a simple counter run from the LM311 pulses as
> the base of a wavetable oscillator. But the LM311 has a linear response,
> so you're going to need a exponential convertor in front of it, in which
> case, you're back to the usual problems of VCO tuning.

Yes, I'm aware of that, and that's OK with me.  I don't need the wavetable
VCO to track any better than a high-quality analog VCO.

> So what's the advantage of the LM311? Why not run the counter from the
> comparator reset pulses of a standard ramp-core VCO, but tuned higher than
> typically? Is *that* the advantage of the LM311 - it can cope with higher
> frequencies?

I think you meant LM331.  However, going back to the datasheet, I see that
it won't oscillate fast enough for my needs, so the question is moot.  To
get 256 steps at 16kHz would require a VCO with a top frequency of 4MHz.  I
think a digital circuit is required here.  I'm just not sure how to do it.