[sdiy] Digital accumulator VCO core?

cheater cheater cheater00social at gmail.com
Tue Feb 9 04:43:39 CET 2021

Hi all,
I was wondering if anyone ever experimented with replacing the
accumulator core with a digital setup. Essentially you would have
control voltage turned into current being shunted to ground, and you'd
sample this current with the ADC, accumulating it in software. A
16-bit, 12 MS/s ADC like the Cirrus Logic WM8196SCDS/V costs only ~$2
- $3 depending on how many you need, and my guess is that this would
be more than enough bit depth and sampling rate to preclude numerical
error. I think this would be able to do FM at audio rate. So does
anyone do this sort of thing?

The nice thing is you don't need to use solid state switches any more,
your switchover is immediate, so no tracking error due to that. Also
perfect for complex wave shapes, you could have a VCO like that easily
output a waveform from a wavetable while still being fully capable of

You might want to use a shunt resistor with bad tempco ... just to
keep things feeling "analog" ...

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