MIDI Association Releases Spec For TRS Jacks

The MIDI spec was released in 1983, and for more than thirty years every synthesizer, drum machine, and piece of computer hardware with MIDI has sported an enormous DIN-5 jack on the back. Why did they choose such a large connector? Well, MiniDIN connectors hadn’t even been invented yet, and today even MiniDIN connectors are rarely-seen, obsolete connectors.

In the last decade, MIDI has found its way into some very small machines. Those Pocket Operators have MIDI sync, you can control a Game Boy with MIDI using the right hardware, and the cute little Korg synths also have MIDI tucked away in there somewhere. You can’t put a DIN-5 jack on those things, leading to some weird implementations of MIDI over non-standard connectors.

Now the MIDI Association has weighed in on the situation. There’s now a spec for MIDI over 2.5mm and 3.5mm TRS jacks. In just a few short decades, you’ll be able to connect MIDI gear with an audio aux cable.

Although there are five connectors in a DIN-5 jack, most implementations use only two connectors to send and receive data. Synth manufacturers have capitalized on this fact and cheap TRS connectors to build their own implementation of MIDI using smaller connectors, sometimes with incompatable pinouts.

Now, though, there’s a standard. For TRS connectors, the tip is pin 5 on the DIN-5, the ring is pin 4, and the sleeve is pin 2. It sends and receives data to synths and drum machines from 1983, and it doesn’t use gigantic connectors.

The only caveats to the new MIDI standard is that 2.5mm TRS connectors are recommended, and that protection circuitry is strongly recommended in the case a headphone driver is inevitably connected to a MIDI device. Other than that, everything’s coming up roses, and this opens up the door to MIDI jacks that are much, much easier to source.

27 thoughts on “MIDI Association Releases Spec For TRS Jacks

  1. Cmon bryan. Not so over dramatic. Never had problems sourcing din jacks. Even sus or seven pin versions. You could at least have mentioned the flimsyness of the 2.5mm jack compared to the more sturdy din-5 and the fact that on stage this will turn into disaster. Its micro-usb all over again…

        1. Who knows … I didn’t have any trouble finding them and I don’t even need any. I probably have at least a half dozen in my stock pile. Some folks just like to be difficult or are not resourceful.

  2. Worst idea ever. There’s a reason why stage equipment uses XLR connectors. They should’ve defined XLR with a unique coding, or industrial RJ11, or something like that, as a replacement for DIN-5.
    And if you need really small connectors, why not defining an USB-C alternate mode for MIDI?

    1. Because that’d require translator chips and complex circuitry to implement USB-c without infringing on the standard.
      Meanwhile 2.5mm mini-jacks are already somewhat common in audio circles for compact microphones.
      USB-c isn’t the be-all end-all connector, but rather a specification for a universal connector used for serial binary data traffic.

      1. > … a specification for a universal connector used for serial binary data traffic.

        Wait … I though that was exactly what MIDI is. *AND* there’s a MIDI endpoint specification in USB too.

        You’re completely right that the USB C connector + associated circuitry would be generally overkill.

        A 2.5mm jack is way more easily sourced and wired up however.

    2. MIDI is opto-isolated digital. XLR is overkill. There’s no need for it. As for USB, you can’t use it to connect (easily) to legacy MIDI devices, just as you can with plain DIN or simple mini-jacks. Don’t forget that you still want to connect to all MIDI devices from the 80s.

      1. THIS. ^^^^^^ optoisolation ftw.
        I wish we just had a like button.
        I already see plenty of this config with the new skool devices that are too small for the DIN connector so the dongle is included. I actually prefer this idea to USB as it always requires a middle man to chatter with my old midi gear.

    3. I think on a stage you would continue to use DIN-5, as it is more robust and reliable than TRS.

      Just for hobby applications, a smaller, more common connector is a good idea, I think

      1. DIN-5 or XLR are too bulky to be included in small equipment like korg monotron. korg volca series have DIN-5, but it eats precious space and i bet designers would not happy about it. so it makes sense to replace it with something smaller.

  3. I see this as pretty big news for the modular synth community. 3.5mm jacks are the standard for the extremely popular eurorack standard and it’s a natural extensions of that standard to use those jacks for MIDI. I’m personally a bit bummed because I’ve designed some hardware using the competing “Arturia” convention which has the signals reversed, but life goes on and this new standard is positive news.

  4. If they would get off of the thin is better there wouldn’t be a problem. I have never had a DIN standard plug or socket fail, fall out, or have to be futzed with like the mini headphone standard. The micro size is just dumber for one silly millimeter less. More fragile and hard to solder up from shop made parts, molded cables are necessary. I will still fight for that jack to plug in on my phone though, as well DIN on any keyboard. Standards have to not change the old but add on new if it causes no problem.

    Common cable connectors create problems on stage or anywhere there is confusion. I have a Digitech guitar processor I got cheap that has standard phone plugs for everything including the effect pedal pot. The effect pot input is dead, I traced it right into the big chip. Poof when some carpet charged static cord or hot death cap guitar amp got plugged into it straight into the big chip.

    1. Both exist, 3.5 is the common one. But 2.5 isn’t completely unknown.

      As the whole reason for this new spec is smaller connectors, the smallest one makes sort of sense. It also lowers the chance plugging in normal audio things.

    2. 2.5mm was most commonly seen a few years ago with headsets for mobile phones. Every millimetre counts! Annoying, but 3.5mm convertors weren’t hard to find (since it was also stereo out, for headphones).

      Now phones seem to have gone back to 3.5mm for headphones, and Bluetooth for headsets. The shitty included wired headsets with most phones don’t see much use.

  5. Yay, my project just got 3mm thinner. For what MIDI needs to carry, switching to 2.5mm TRS jack will work just fine. Sure, it might come out easier, but if you didn’t have a locking connector to begin with, what’s really the difference.
    Frankly I’d rather have a connector which comes out when my stuff moves enough to make it. Saves me from taking said keyboard apart again, scraping back some more PCB to add yet another blob of solder where the jack is tearing off the board, yada yada yada..

  6. What am I missing here?
    I thought one of the good things about MIDI was the isolation between devices.
    Cable shield only connected at source end. Opto’s to isolate.
    Not isolation for protection, isolation for ground loops.
    A 3 pin connector ties units together. A 4 pin 2.5 or 3.5 would be preferred.

      1. Indeed. The standard MIDI receiver implementation has the “current source” and “current sink” lines connected directly to the diode in an optoisolator. What connector is used is immaterial.

  7. Hoorraay, let’s open the door for scrappy cheap prone-to-wearout TRS connectors and subscribe to flaky, intermittent connections!

    Every other application domain of connectors also regrets the typical consumer grade throw-away quality of TRS too.
    There was a reason why better Walkmen sported dual headphone sockets; partner listening was just spin-off: wearout the main one.
    So will TRS blessed MIDI gadgets also come with dual connectors? I fear not…

    1. Yeah, unfortunately. I’d hope this market doesn’t all go for TRS, but since it’s generally geared toward more serious commercial grade gear, perhaps it’s likely to only add an option for a less reliable, smaller connector in select circumstances.

      To be fair, it sounds like the standard was made because some companies were doing it anyway, and the lack of standard pinout was causing headaches in the industry, so I’m guessing it’s overall a good thing that the standard was made.

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