[sdiy] Chopper circuits for audio and CV?

[cheater cheater]

On Wed, Jun 2, 2021 at 12:26 PM Roman Sowa <modular at go2.pl> wrote:
>
> Does that sound like "let's use synth-diy for effortless free
> feasibility study" call?

Of course! Why else post to the list? :-)

> Noone can say rough figure without going through draft design and parts
> selection. I'd say anything between 20 and 200 USD for a pair of
> 16-channels I/O in low quantities.

Thanks. That's not little!

> Roman
>
> W dniu 2021-06-02 o 12:06, cheater cheater pisze:
> > 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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