[sdiy] Chopper circuits for audio and CV?

cheater cheater cheater00social at gmail.com
Wed Jun 2 12:06:09 CEST 2021


OK, but what could the price be per I/O pair of 16 voices? I'm trying
to picture the total costs here.

On Wed, Jun 2, 2021 at 11:58 AM Roman Sowa <modular at go2.pl> wrote:
>
> I would say, not that far pricewise from total analog solution with
> comparable specs. Not even sure which one would be cheaper.
> Either it's 10 units or 5000 units, the price ratio remains.
>
> Roman
>
> W dniu 2021-06-02 o 11:40, cheater cheater pisze:
> > If you wanted to use ADAT or something similar, how much do you think
> > it could cost if you had 50 outs and 50 ins, where each one has to
> > convert 16 analog synth channels to digital, or back from digital to
> > 16 analog channels? Assume something competent like 16-bit audio and
> > 18-bit CV*
> >
> > And what if you scaled this up by 100?
> >
> > * actually I'm not sure - what's a competent bit depth for CVs? Say
> > for something like pitch tracking on a self-oscillating filter.
> >
> > Cheers
> >
> > On Wed, Jun 2, 2021 at 11:30 AM Roman Sowa <modular at go2.pl> wrote:
> >>
> >> That was covered on this list inside out. There were ideas for using
> >> band shifting aka AM, and also pulse displacement technique known from
> >> RC toys, and I'm nearly sure TDM was also discussed few times. Everytime
> >> the outcome was: it's easier to do in digital and results of doing it in
> >> analog are far from satisfactory, not to mention insane complexity of
> >> the circuit.
> >>
> >> Of all methods discussed so far TDM seems like most natural and easiest
> >> to do. Done in every polysynth known to mankind in terms of CV, but for
> >> audio - that could get tricky. You'd need sample&hold circuits able to
> >> track and settle in less than 1us and still expect a lot of noise and
> >> possibly distortion. And that's for mere 48ksps of audio channel.
> >> No need for separate clock cable, you can regenerate clock from TDM
> >> signal. Might even add some pattern to it to mark synchronization of 16
> >> channels.
> >>
> >> Why not use something like ADAT instead?
> >>
> >> Roman
> >>
> >> W dniu 2021-06-02 o 09:58, cheater cheater via Synth-diy pisze:
> >>> Hi all, I was wondering if anyone ever tried using a chopper circuit
> >>> to put 16 voices of full bandwidth audio over one 1/4" cable. Also,
> >>> the same thing goes for CV. Is that a feasible use case? What are the
> >>> biggest problems that could be encountered here? I assume that the
> >>> chopper clock can be distributed separately using a 50 ohm terminated
> >>> distribution.
> >>>
> >>> Thanks
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