[sdiy] simulate detune / polyphony with a single DCO

[S Ridley]

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

There was also the Moog SL-8, which never went into production, a 1
DCO/voice poly boasting a "variable harmonic multiplier" (VHM) with
detuning and sync sweep effects.

Steve


On 10 April 2017 at 00:04, Tom Wiltshire <tom at electricdruid.net> wrote:

> 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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