[sdiy] Digital accumulator VCO core?

Brian Willoughby brianw at audiobanshee.com
Fri Feb 12 06:18:22 CET 2021

On Feb 10, 2021, at 08:24, Aaron B. wrote:
> This also makes me think of the Poly 800 tone generator - four square
> waves at different octaves, each switchable on/off, and a square/saw
> switch that simply adjusted their relative amplitudes. I've often
> thought of cloning it with a 4 bit digital divider and a standard VCO
> clocked 16x higher than normal. Going "backwards" with a triangle
> frequency doublers might work as well and be easier to tune, at the
> cost of more parts.

Isn't the Poly 800 circuit just a cheap 4-bit DAC?

You could use a CMOS divider that has all of the intermediate bits on individual pins (some dividers skip a few bits, so they're no fun) and hook up a DAC with way more than 4 bits. Of course, you'd have to clock the VCO a lot more than 16x the desired frequency.

Brian Willoughby

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