It seems that every time I start to wire-up a MIDI socket or plug I’m looking up, yet again, both what goes to pin 4 and pin 5, and also which pins on a MIDI socket are pins 4 and 5!
So I thought I’d hunt around once and for all for everything I can find on the topic and put it in one place. This is the result.
You can download a single sheet version of this post here:
- SDEMP – MIDI Connections Cheat Sheet (PDF format)
Note! Everything here is presented on a “best efforts” basis. Use it at your own risk. I accept not liability or responsibility for the information presented here!
Always consult the official specifications:
MIDI Manufacturers Association / Association of Musical Electronics Industry
MMA Technical Standards Board / AMEI MIDI Committee
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- CA-033 MIDI 1.0 Electrical Specification Update (2014)
- RP-054 Letter of Agreement for Recommended Practice – Specification for use of TRS Connectors with MIDI Devices (2018)
See midi.org for details.
The Basic MIDI Circuit
Key points:
- A MIDI circuit is a 5mA current loop.
- The MIDI IN circuit is opto-isolated.
- When TX pulls LOW in the transmitter, current flows through the opto-isolator in the receiver.
- Cables are a shielded twisted pair.
- The cable shield is connected at both ends in the plugs.
- Ground is only connected in the OUT socket. There is no ground connection in the IN socket.
- The extra diode is protection against getting the wiring wrong (or a dodgy lead)!
For a detailed but accessible analysis of the MIDI circuit operation see Notes and Volts “MIDI For the Arduino”.
MIDI OUT Connections
MIDI IN Connections
MIDI TRS
For MIDI TRS:
- Ring = 4 = Current Source
- Tip = 5 = Current Sink
- Sleeve = 2 = Ground
Compare to a Stereo Audio Connection:
- Ring = Right Channel
- Tip = Left Channel
- Sleeve = Ground
Kevin
Simple DIY Electronic Music Projects 