[sdiy] Innovative Oscillator Design (or not ?)

[cheater cheater]

I'm having trouble understanding how it is different from a juno alpha
style DCO. i get that it's different, i just don't know how.

On Tue, Apr 9, 2024 at 10:45 AM Roman Sowa via Synth-diy
<synth-diy at synth-diy.org> wrote:
>
> This is not doable with simple PWM. You talk about closed loop control,
> but then it will have to make huge corrections from cycle to cycle,
> leading to blurry, modulated waveform. Assuming 10kHz range, the low end
> using 8-bit PWM is like 40Hz, and next step is one octave higher. To
> make it work you have to constantly measure the VCO output voltage and
> not just the cycle period and adjust PWM multiple times during single slope.
> The slopes of the triangle will not be smooth anyway, but steppy. The
> steps will have the slope the same as the highest frequency triangle,
> that is when PWM is at 100%.
> PWM frequency is independent of VCO frequency, so at some frequencies
> you might expect intermodulation that will blend all over audio band.
>
> Interesting idea and I don't hink I have ever seen it, although it
> highly resembles switched capacitor filter. Who knows, maybe there is a
> way to use commercially available switched cap filter ICs to work as
> VCO. But IMHO there is a lot more other simpler options to make VCO.
>
> How about using common $2 Sigma-Delta DAC to control the integrator
> switch? It makes it so much easier. Wide range precise control of 24
> bits, every note is kept stable with single write to the DAC. The MCU
> only writes the DAC on pitch change, and possibly check tuning from time
> to time but it will not drift at all if you use proper integrator parts.
>
> Roman
>
> W dniu 2024-04-09 o 08:52, M J Bauer via Synth-diy pisze:
> > Attn: Synth-DIY community...
> >
> > A while back (2022), I had an idea for an oscillator design which could
> > be used in modular or hybrid synth's, but I have not yet tested the
> > concept. The oscillator may be digitally controlled or voltage
> > controlled, or both at once. I'm not sure if this technique has already
> > been tried and proven. I haven't seen any evidence of it, so I would be
> > grateful if anyone with a greater knowledge of the art can tell me if
> > this is a novel idea, or a concept that has appeared before. (See
> > attached summary.)
> >
> > M.J. Bauer
> >
> >
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