[sdiy] Mitxela combined knob & socket

[cheater cheater]

I've seen it when it came out. It's a fun exercise but not the
smartest when it comes to manufacturing and extensibility.
Manufacturing those machined minijacks and fitting them to knobs would
be a nightmare unless you made a machine to do exactly that, and even
then, the fitting and gluing of the magnet will have to be done by
hand.

For one thing, making concentric gears isn't that difficult. One could
go around the minijack as well. A gear could be powering a mating gear
on a potentiometer.

On the other hand, if you want to go with the minijack thing, it would
probably be best to use simple voltage anyways. Use a TRS or TRRS jack
and add voltages on the new contact / contacts. So for example TRRS =
input, GND, 12V, -12V. Or whatever your synth uses for voltage rails.
Or if it's a depth knob, then whatever is normalized. At that point
you can just use a normal potentiometer. That said, it wouldn't be as
mechanically stable if you *just* use the minijack as mechanical
mounting. You can always add a mechanical key such that the minijack
knob slots into it, and then when it turns, it uses that interference
fit for leverage. Easily done with a bent-tab washer.

Here's the nice thing about that last one. The PCB that holds the
3.5mm plug and the potentiometer can have *another* jack on it. Plug
it in and you have a depth knob, or offset knob, or exponentiation
knob, or shaper knob, which could be switchable by, yes, a switch on
that pcb. All powered by the voltages present on the TRRS jack.


On Mon, Jun 9, 2025 at 9:13 AM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> The mechanical-only solution he mentions at the end did appear in the 60s.  I can't remember if it was for the BBC or EMI, but AB Electronics in South Wales made a combined 1/4" jack with a switched resistor network using a large knob around the jack socket.  It was used for setting the input stage gain of amplifiers on audio mixers.
> ________________________________
> From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Ben Stuyts via Synth-diy <synth-diy at synth-diy.org>
> Sent: 09 June 2025 01:44
> To: SDIY List <synth-diy at synth-diy.org>
> Subject: [sdiy] Mitxela combined knob & socket
>
> This is just great: https://youtu.be/dLw2QQdOLaM
>
> I’m not sure how useful it would be in practice, or how wel it would stand the test of time. (As he says so himself.) But I’m very impressed by the concept. One of those things that seems obvious once you’ve seen it, but being the first to come up with this is extremely impressive to me. Or has anything like this been done before?
>
> More info here: https://mitxela.com/projects/euroknob
>
> Ben
>
>
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