[sdiy] VCO - sine output - why bother?

[Vinicius Brazil]

My dual core Cerberus works in this manner.

On Fri, Aug 26, 2016 at 8:59 AM, <mskala at ansuz.sooke.bc.ca> wrote:

> On Fri, 26 Aug 2016, Quincas wrote:
> > Is there not a way to make a sine core oscillator and derive the other
> waves
> > from it? Like a filter with fixed high resonance for the sine, a
> comparator
> > for the square etc...
> > Why doesn't anybody do that?
>
> I think the sawtooth is tricky to do by waveshaping, and the triangle
> isn't trivial either.  But just today I was thinking about a hybrid
> design:  have the exponential converter generate two duplicate currents,
> one drives a sine core, integrate the other for a sawtooth, but don't use
> a comparator on the sawtooth for resetting the integrator.  Instead, use
> the zero crossings of the *sine* core to decide when to reset the sawtooth
> core's integrator.  That way reset time doesn't affect the accuracy of the
> sawtooth's tracking.  The triangle shape would most naturally come from
> rectifying the sawtooth (with the usual glitch of doing that).
>
> This would not necessarily be better overall than a more conventional
> design, but it seems like it would at least have *different* issues, and
> would be fun to try.
>
> --
> Matthew Skala
> mskala at ansuz.sooke.bc.ca                 People before principles.
> http://ansuz.sooke.bc.ca/
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