[sdiy] simulate detune / polyphony with a single DCO

[Tom Wiltshire]

Assuming I'm understanding what you're intending, I've come across a couple of similar things, although not the same;

One is the DCOs with Sync on the Minod Vorga (a short-lived MIDI mono synth with several interesting features). These allowed a "Wave shape CV" to produce a Sync Bend on a single oscillator by increasing the control current to the integrator, whilst using the MCU to detect a integrator reset using a on-chip comparator as a normal VCO would. The oscillator reset could then either be triggered by the timer or the comparator, both inside the MCU. This basically gives you the effect of two oscillators with only one. The "Sync Master Osc" is sort-of hypothetical.

The second example is the Arp/Rhodes Chroma, which included a "detuned ramps" waveform which was actually generated using a PWM pulse added to a ramp waveform, IIRC. Again, the effect of two oscillators with only one. Closely related to some of the "Ramp animators" that exist out there.

I'm assuming that by "detuning", you're meaning the beats between two oscillators, right? Obviously one oscillator on its own can be hopelessly out of tune, but that's not the same thing.

In short, no, I don't think you're likely to be doing anything stupid, and yes, similar things might have been tried, but not often enough to mean it isn't totally worth doing right now.

HTH,
Tom



On 9 Apr 2017, at 23:23, Chris McDowell <declareupdate at gmail.com> wrote:

> 
> Howdy list, 
> 
> I've been playing with DCOs, and am realizing that detune or even polyphony (which would end up paraphony I guess) could be achieved with a single DCO. The idea is to use two timers in a microcontroller, pulsing the same pin that's used to reset the DCO's integrator. A built in DAC from the micro controls the rate of the integrator, and as detune increased, would adjust the slope. I have a PCB on the way to test all this out, looks good in LTSpice. 
> 
> Anyone heard of this being done before? Are there any glaring dumb oversights?
> 
> Cheers! 
> Chris 
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