If you are working in Electronic music you will likely be familiar with MIDI, the Music Instrument Digital Interface. In its earliest incarnations, a 5 pin DIN socket was used. But since it is a digital protocol, it can be transmitted over different mediums, such as USB cable or commonly in small DAWless devices, 3.5mm TRS cable.
What is TRS?
TRS stands for Tip – Ring – Sleeve. Where as shown in the diagram, a 3 wire cable is terminated on the 3 different connector parts. This is the same cable used for stereo headphones. But wait, MIDI DIN has 5 pin sockets. This is true the original MIDI standard used 5 pin to allow for future expansion, such as carrying power on an extra pin, and also the cable type provided robustness. However the MIDI 2.0 standard only requires the use of 3 pins, hence in small DAWless equipment the ‘3.5mm headphone socket’ or TRS standard has been adapted.
TRS A vs TRS B
Manufacturers started using TRS MIDI in their equipment before it was completely standardized, and hence unfortunately there are two different common wiring formats referred to as TRS-A and TRS-B. The MIDI 2.0 standard uses TRS-A style and modern devices such as Korg and the Roland Aira T-8 and S-1 use this. However Arturia and Novation had already settled on TRS-B for synths such as the Arturia Microfreak and Novation Mono Station. However note that some newer Novation devices such as the Launchpad pro mk3 is now using type A! So always check the manual for which kind it is!
TRS Adaptors
So in order to connect a device with a MIDI TRS socket to other equipment with MIDI DIN, you require a 3.5mm to MIDI DIN adaptor TRS Adaptor cable, that has been wired up to match the standard your kit is using.
as an aside, I purchased a cheap TRS-B adaptor for my Novation Mono Station and found it did not work. So I tested with a multi-meter using the above diagram and found out it was in fact a TRS-A that had been shipped to me!
3.5mm TRS cable
One advantage of TRS sockets aside from the small form factor is two devices with the same standard, such the Roland Aira range can be connected together via MIDI just by using stereo 3.5mm TRS cables. No need for any funny adaptors
Crossing Over
However if you wish to connect a TRS-A and TRS-B device together, either each requires a TRS adaptor and a MIDI DIN cable in the middle, or you would need a 3.5mm TRS cross-over cable which swaps the RING and TIP. This is some what of a niche use case, but they are available to purchase or you could make your own if you are handy with a soldering iron.
Gear featured in this article
MIDI TRS breakout cable Type A
MIDI TRS breakout cable Type B
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