[sdiy] How to use an analog time-domain multiplexer?

cheater cheater cheater00social at gmail.com
Sat Jun 5 01:41:11 CEST 2021

On Fri, Jun 4, 2021 at 7:28 PM dh at atoav.com <dh at atoav.com> wrote:
> On 04/06/2021 16:37, cheater cheater via Synth-diy wrote:
> > I'm not completely discounting having something like an impedance
> > matched transmission line for the signalling. One thing that I wonder
> > about is, though: what happens if you take the output of a normal euro
> > rack synth - either audio or CV - and feed it into such a
> > low-impedance input? Say the input is 50 Ohm, 300 Ohm, or 600 Ohm. I
> > don't really know what typical output impedances are in Eurorack. And
> > it would be nice to be able to patch a mono Eurorack module into the
> > polyphonic input of this thing.
> If that isn't even the intention why don't you just go for a more
> suitable cable/connector? Just take a regular CAT-7 cable. In addition
> to being cheap and readily available you'd have 4 twisted pairs which
> are shielded, which would be a much better thing to consider than using
> regular audio cables of questionable quality.

There's a couple of reasons.

1. RJ-45 plugs break very easily when being patched and unpatched
2. the cable is very thick, even the stranded kind, and unwieldy, but
that's not really /so/ bad
3. it's hard to patch and unpatch an RJ-45 cable with one hand and it
requires considerable free space around the connector to do that,
which takes up panel space
4. no panel mount jacks
5. can't be stacked
6. it would be nice to be able to use the same input jack for
multiplexed polyphonic audio, and for mono audio. Might need a switch
for the input impedance, but that's all really. Mono audio should get
demultiplexed to 16 copies of the same thing, basically like a
distributor amp.

> I can already picture people mailing you and telling you how with
> _their_ cable it didn't work. If you don't gain anything from using a
> audio cable, why would you?

Yeah, I can see that being the case.

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