MIDI cable length / DIN to XLRs

[Gizmo1977]

I've always read that MIDI could be sent through DIN connectors to a distance about 15m.
I've already soldered DINs which are a pain to work with (I prefer soldering VGAs before those connectors, believe me).
The other day I read about a trick that I want to know how reliable and true is it:
- Buy a MIDI cable from the store (1m or so)
- cut it in half
- add XLR connectors to each end.

Now you can use regular XLR cables as extenders.
So... is the story as beautiful as it's told?

A regular audio XLR cable might not work properly with MIDI signals?
Would length be compromised?

Thanks in advance.

P.S. The devices I must link just use DIN connectors for MIDI and the distance would be around those 15m.

[The Elf]

Cutting MIDI cables in half and soldering on XLRs will definitely work. I have a few of these cables to let me connect up keyboards over mic connections between control room and studio. I've also used daisy-chained mic cables to extend.

As to cable length... I guess that's simply up to the quality and resistance of the cable used. I've gone well over 15M on occasions with no problem, but I guess there will be a limit at some point.

[Hugh Robjohns]

Yes, you can run MIDI over mic cables, and chopping up a commercial MIDI cable to fit XLRs avoids the challenges of soldering DINs (although I dont find them particularly difficult to work with).

The fundamental frequency for MIDI data is around 31kHz, and since it's digital data passed as square waves it needs several odd harmonics above that. So the signal has a much higher bandwidth than analogue audio.

This means cable capacitance is critical and needs to be kept as low as possible. And since capacitance is related to cable length the cable lengths needs to be as short as possible, too — but 20-25m should be quite practical as long as you don't use starquad mic cable!

Cable intended for AES digital audio, or CAT5 (etc) works very well and will allow extended cable lengths.

In terms of XLR connections:

DIN 4 — data + — XLR 2
DIN 5 — data - — XLR 3
DIN 2 — screen — XLR 1

Some MIDI cables are wired with a quad core cable and all 5 pins connected. If so, DIN 1 and 3 (the two outer pins) are left unconnected and insulated inside the XLR.

[Gizmo1977]

Thanks, The Elf and Hugh!!

What would be the issue if quadcore cable was used? Double the capacitance and half the distance?
Even of 1 and 3 are left unconnected?

Thanks again!!

[Hugh Robjohns]

If you're talking about the DIN cable, it shouldn't make any significant difference with its two-core or four-core.

[Gizmo1977]

Sorry for my English but I understood that if you used quadcore cable would reduce distance.

"but 20-25m should be quite practical as long as you don't use starquad mic cable!"

[Hugh Robjohns]

Star-quad is a specific type of mic cable which is designed to minimise interference in one specific situation... and people often choose it thinking it's better, when it usually isn't.

In the case of MIDI adapters, star-quad has very high capacitance which will greatly reduce the workable cable length.

[Gizmo1977]

Thanks!!