Are all 5-pins of a midi cable that important to be wired?

Here is the pin-out (note that the pin-out is not in numerical order, it is pin# 1, 2, 5, 4, 3 left to right):

http://www.colomar.com/Shavano/midi1.gif

Pin 5 = current sink
Pin 2 = shield
Pin 4 = current source

As long as the wiring is contiguous between each pair of pins (5 to 5, 2 to 2, 4 to 4), the signals being carried on 5/2/4 don’t matter.

I’ve seen a manufacturer use one of the null pins (1 or 3) as a ground point for a sheath-ground-path at one end of the cable (presumably to shield RF and send to ground).

Bingo! MIDI cable connector is a German 5-pin DIN (Deutsches Institut für Normung)-connector. These used to be popular connectors on European HiFi-equipment (hey … 5 pins give you stereo in/out in one connector … simple and clever).

More information:
http://en.wikipedia.org/wiki/DIN_connector

I have an old ADA MP-2, a midi controlled tube guitar pre-amp. The foot switch for it sends midi signals to the pre-amp and can use midi phantom power sent by the pre to the foot selector switch. The other two pins are for this midi phantom power. These are the only devices I’ve ever seen that use all five midi pins.

The Ground Control, a live foot MIDI controller and processor also used the unused pins to transmit power to the device, reducing your on stage cable count.

I suppose to sum up, if you want guarantee 100% MIDI compatibility with all devices, then all 5 pins should be wired. If not, and some day some piece of gear just isn’t working right, it will always be gnawing in the back of your mind that it might be the problem - even if it’s not. Even worse if it is the problem and you forgot that some of your cables are not fully wired.

Just FYI,
The Behringer CT100 cable tester is pretty cheap and includes midi cables in it’s repertoir.
I find it indispensable, even puts out a couple of test tones.

I would disagree. Only 3 pins are standard. If device is using all 5 the 2 “non-standard” pins may have been wired to anything. If you connect 2 devices with different pin-outs together with 5-wire cable, you may have problems (or even smoke, if you’re unlucky). Anyway. I’ve always used 5-wire cables and never had any problems.

Never buy cheap cables! It’s easy to roll your own. Just wire up those MIDI DIN connectors with three phase Romex … 10 gauge. :wink:

In that case the device is using custom midi cables so is itself not midi standard, and should specify this with a warning to the effect, for if one connects with a standard midi cable, chances are good its 5 conductor wired pin to pin. I too have only ever used 5 conductor cables I’ve tested all of mine and I purchased them as midi cables.
Perhaps I should have phrased my original statement to say ‘100% MIDI compatibility with all 100% MIDI compatibile devices’.