How to Wire a MIDI Cable Using DIN Plugs

Make up DIY Synthesiser Digital Interface Connections

May 3, 2009

MIDI cables are readily available in standard lengths, but for short lengths and rack wiring it sometimes makes sense to wire up bespoke lengths on-site.

MIDI uses standard 180 degree five pin DIN connectors, and the cables are easy enough to make up for odd lengths and for fixed wiring installations. The standard is defined in terms of using shielded twisted pair, with the shield connected to DIN plug pin 2 at both ends.

However, it is usually expected that ground is not connected at the MIDI IN connector. This is to prevent ground loops between equipment - MIDI is designed to be balanced, and an optoisolator is preferred for the internal circuitry attached to the MIDI IN connector. However, none of this affects the wiring of the DIN cables, where pin 2 should be connected to the cable shield at both ends. It is the job of the attached MIDI devices to sort our which end of the cable shield is actually connected to anything.

Shielded twisted pair is commonly used in audio for balanced connections in professional gear, and standard balanced microphone cable will work fine. The maximum cable length permitted in the MIDI spec is 15 metres (fifty feet).

The plugs are wired 1:1, ie pin 2 to pin 2, pin 4 to pin 4 and pin 5 to pin 5. This is not the same as a typical tape recorder lead of the type commonly used in hi-fi equipment made in the 1970s, where the signal carrying pins were crossed over, so although such a cable will look similar to a MIDI cable it will not work as such.

Parts Needed to Make up a MIDI Cable

the following items are needed to make up a MIDI cable. If the cable is for fixed use, the cheaper plastic-covered plugs are fine. However, for stage use the metal-shelled plugs are to be favoured, because it is easy to crush the plastic-shelled plugs by standing on them!

MIDI Cable DIN Pinout

This is how the pins are connected on the MIDI DIN plugs (identical at both ends of the cable)

The pinout of the DIN plug is not particularly intuitive - this is because the 5-pin DIN plug as used for stereo go and return was introduced for stereo in the 1970s. the previous tape recorder interface plug was a three-pin 180 degree version featuring just pins 1,2 and 3 which were logically allocated. See the diagram for how the pins are allocated.

Wiring the MIDI cable using DIN plugs

The cable shell needs to be pushed onto the cable first, then wire the pins in the specified manner. Pay particular attention to keeping the braid isolated from pins 4 and 5 - it is easy for stray whiskers of the braid to short adjacent pins. Insulating sleeving on the braid may help there.

Solder the pins carefully - the plastic holding the pins is soft and melts easily. Putting the plug into a spare socket can help keep the pins from splaying, the socket should of course not be one on a piece of equipment.

References

The copyright of the article How to Wire a MIDI Cable Using DIN Plugs in Music Technology is owned by Richard Mudhar. Permission to republish How to Wire a MIDI Cable Using DIN Plugs in print or online must be granted by the author in writing.