[sdiy] Best way to wire up a multi-channel cable?

[Tom Wiltshire]

In which case, there's no effect from long cable runs. You've only got short cables, and they'll be driven by active circuits each time. It's not like trying to send audio down a 100m wire and then pick it up at the other end where cables losses and capacitance become a major consideration.

The cumulative effect of the multiple circuits would be more of an issue for noise than the short cables between them, I'd have thought.


> On 21 Apr 2025, at 11:01, cheater cheater <cheater00social at gmail.com> wrote:
> 
> circuits inbetween. like any modular.
> 
> On Fri, Apr 18, 2025 at 6:16 PM Tom Wiltshire <tom at electricdruid.net> wrote:
>> 
>> Does it go through ten one after the other, or does it go through ten with circuits in-between?
>> 
>> 
>> Also what are those plugs on that Tip-Top thing? Looks like banana jacks, but....
>> 
>> 
>> 
>>> On 18 Apr 2025, at 05:55, cheater cheater <cheater00social at gmail.com> wrote:
>>> 
>>> i mean, it's for a modular. so a single cable won't be long, but the
>>> signal doesn't just go through one cable, it will go through ten.
>>> 
>>> tip top are doing something similar and i believe they're doing
>>> balanced as well.
>>> 
>>> https://tiptopaudio.com/art/modules-details/
>>> 
>>> On Thu, Apr 17, 2025 at 7:54 PM Tom Wiltshire <tom at electricdruid.net> wrote:
>>>> 
>>>> I don't claim to be knowledgeable on this topic, but I did spend time with a chap who was! He worked for a company making front-of-house equipment for the professional market. In that arena, all multi-channel audio is done digitally these days, for the reasons you've enumerated. The fat "snake" that used to go from the stage to the front-of-house desk is now a much-skinnier digital link carrying endless channels of high-resolution audio.
>>>> 
>>>> If I wasn't going to do that, I think I'd be extremely inclined to keep it as simple as possible. The distances you're talking about are short or very short. It's not going to be balanced audio. Do you even need line drivers and receivers? If so, why?
>>>> 
>>>> HTH
>>>> 
>>>>> On 17 Apr 2025, at 02:33, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
>>>>> 
>>>>> Hi all,
>>>>> I want to create a cable that carries 16 channels of audio. The
>>>>> connectors on each end have 20 pins each available, so not quite
>>>>> enough to run balanced. My best guess is to run 16 channels
>>>>> single-ended + reference, but I'm not sure how to best create the
>>>>> transmitter and receiver such that EMI gets minimized. I was wondering
>>>>> if someone was knowledgeable enough to point me in the right direction
>>>>> towards technical materials that analyze this sort of situation, as I
>>>>> bet it's something that's been done before.
>>>>> 
>>>>> The cables will be short - between 15cm and 50cm, with 2m being the
>>>>> maximum - but I want to be able to retain good audio quality, prevent
>>>>> ground loops, etc. This is a situation similar to a patch bay or a
>>>>> modular synthesizer so while each run is short, total runs will be
>>>>> long and will have loops in them as well as signals branching and
>>>>> joining. Look at some examples of [complex modular
>>>>> patches](https://www.google.com/search?q=complex+modular+patch&udm=2)
>>>>> to know what I mean.
>>>>> 
>>>>> The one thing I was thinking of was:
>>>>> 
>>>>> - use pins 1-16 for each channel of audio
>>>>> - use pin 17 to carry a reference voltage
>>>>> - on the transmitter, take ground-referenced audio channels from the
>>>>> internal circuits and add the voltage of pin 17 to them, then take
>>>>> that summed output and put it out via the relevant pin (1-16). Call
>>>>> the node with pin 17's voltage that is being added to all others the
>>>>> "reference node".
>>>>> - on the receiver, take input channels 1-16 and subtract pin 17 from
>>>>> them. Again call pin 17 the reference node.
>>>>> 
>>>>> That can be done using a bunch of op amps, but my biggest concerns
>>>>> are, as follows:
>>>>> - loading down the reference node in the transmitter, and with
>>>>> resistor or op amp differences, sending out channels (1-16) that are
>>>>> each biased to a slightly different voltage.
>>>>> - loading down the reference node in the receiver and component
>>>>> differences as above, therefore recovering shifted versions of
>>>>> channels 1-16.
>>>>> - having high impedance on both input and output, making the cable an
>>>>> antenna so it picks up EMI very easily
>>>>> 
>>>>> I would appreciate any suggestions.
>>>>> 
>>>>> Thanks!
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>>>> 
>>