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I understand that I'm not suposed to use mic cable for DMX sygnal. And that's the reason why the standard mandates 5-pin XLR connectors.
I also know that in practice 20 out of 20 events I've witnessed here in Ukraine used mic cables, and all the gear had 3-pin XLR for DMX.
I currently own an installation of DMX console and 8 PARs, connected with 1*6 + 7*3 meters of mic cable with 3-pin XLR connectors. It works seamlessly, no visible glitches whatsoever.

My question is purely practical: I want to connect another piece of equipment at 5 meters from the end of the aforementioned sequence of PARs. And I want to do it with Cat5 cable, as it's both cheaper and more appropriate as per standard.

Would it work? Or would it work better/more reliable if I use mic cable for the extension?

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  • \$\begingroup\$ The difference may be the shielding benefit of mic cable for EMI rejection. CAT5 offers balanced differential signals but no shielding to common mode interference. If each channel has it's own cable, you might use spare wires as ground to provide some reduction on external impulse noise, but grounded at one end only to avoid possible ground loop noise. I assume sender and receiver have built in differential terminators. THe goal is to shunt common mode noise and a balun is used for Ethernet to achieve this by raising CM impedance rather than shunt to ground. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 30 '17 at 17:05
  • \$\begingroup\$ A mic cable shield surrounds the signals and shunts the stray noise to ground. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 30 '17 at 17:05
  • \$\begingroup\$ I was going for sFTP, still 2 times cheaper than the cheapest mic cable \$\endgroup\$ – Gleb Jan 30 '17 at 17:24
  • \$\begingroup\$ got a datasheet? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 30 '17 at 21:32
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CAT 5 is acceptable, but how it will interact with the rest of the mic cable (Generally about 60 ohms differential or so) is a bit anyones guess, but it will not likely make things better, especially as I suspect you also don't terminate, and some of that kit may or may not be using proper RS485 line RXs?

For me, doing this with mic cable rates an invitation to Murphy, who as we all know is always watching. IME it is the sort of thing that typically works just fine until the audience comes in, at which point you loose control of the blinders and strobes...

If I had to go here for some reason I would use mic cable for the extension, simply because it avoids an extra impedance discontinuity, and I would terminate with something closer to 60 ohms then the usual 110, to match what most mic cable tends to be, but there is a reason most of my 'mic cable' stock is actually 110 ohm AES digital audio cable (Which handles DMX just fine).

End of the day you are looking at ~30m of cable total which is a very short run as these things are measured, but you are operating well outside the defined standard, so no guarantees of anything much.

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