Last newsletter we explained the difference between 5 pin and 7 pin midi cable however we should have explained a bit better as we got some email back from folks. Here was the original explanation:
“5 pin MIDI cables are the only real standard however many manufacturers have been using 7 pin connectors as an extension to the standard to allow phantom powering of MIDI controllers. The key is that the pins on a 5 pin connector line up exactly with 5 of the 7 pins on a 7 pin connector. The first 5 pins carry the MIDI data and the extra 2 carry the phantom power. If your devices both have 7 pin MIDI connectors you can use a 7 pin MIDI cable and have one phantom power the other. If one device has a 5 pin connector or if you choose NOT to phantom power, you can use a standard 5 pin MIDI cable and everything will still work. You’ll just have to power your MIDI controller with your own adapter. If you are phantom powering, make sure that your two devices are compatible. Unfortunately different manufactures use different phantom power voltages.”
To (hopefully) clarify: even though MIDI specifies a 5-pin connector, only 3 of the pins on a 5-pin MIDI connector are actually carrying data, and the third pin of those three is a ground that’s typically used only for shielding. This leaves two pins unused. We (and other manufacturers like Fractal Audio) use these two pins for a second stream of MIDI data going in the opposite direction. This allows the Axe-Fx – and our switching products – to have two way communication with the Mastermind GT.
Other manufacturers use the extra two pins in a 5-pin MIDI connector to provide phantom power over a 5-pin connector. We prefer using the 7-pin connector approach because it prevents phantom power from being passed to a device that isn’t expecting it. To the best of our knowledge, all devices that have 7-pin MIDI connectors accept or send phantom power.
This may make things seem more confusing, but it shows the need to be very careful when dealing with phantom power. With no standardized way to do it, you need to make sure you have the correct cables and voltages for your devices. If you have questions, please let us know and we’ll do our best to help!