[sdiy] Chopper circuits for audio and CV?

Roman Sowa modular at go2.pl
Wed Jun 2 12:26:37 CEST 2021


Does that sound like "let's use synth-diy for effortless free 
feasibility study" call?

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.

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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