[sdiy] VCO - sine output - why bother?

[Donald Tillman]

> On Aug 26, 2016, at 4:59 AM, mskala at ansuz.sooke.bc.ca wrote:
> 
> 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 Aries VCO, designed by Dennis Colin (who was responsible for much of the early ARP synths), did something very similar.  It had an exponential converter with twin outputs, one for a triangle wave core, and one for a separate sawtooth wave.  And the peak of the triangle wave reset the sawtooth wave.

Details here:
    http://modularsynthesis.com/aries/AR-317/ar-317.htm

And within that:
    http://modularsynthesis.com/aries/AR-317/Aries%20AR-317%20VCO.pdf

Note that the Aries design still has the sawtooth and triangle 90 degrees apart.  Resetting the sawtooth on one the triangle's zero crossings would align them.

  -- Don

--
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com