[sdiy] Who apart from me things the whole MIDI board needs replacing ?
mr at analogue.org
Wed Jan 26 20:38:22 CET 2022
Tom Wiltshire <tom at electricdruid.net> skrev:
> So does the 3.5mm TRS MIDI not-Standard connect the ground of the TRS lead
> at both ends, or only one like DIN MIDI? And does it use opto-isolation in
> the same way?
> If so, it's basically just a change of connector for something of a
> smaller size and I don't see any problem with it. If the good features of
> the original standard also got dropped in the change, that seems like a
> somewhat retrogressive step.
> While I can see that if everyone was using 3.5mm perhaps it made sense for
> the standard to reflect that, 3.5mm is alos used for audio input/output on
> a gazillion devices and people are absolutely bound to try connecting it,
> just to see if it works. 2.5mm is less common and prevents that to some
The specified cable for TRS MIDI is shielded twisted pair, why it kind of
makes sense to specify a non-audio-standard connector for it, so that
people don't just take any eurorack cable. (Who would do such a thing?) .-)
There are some interesting passages in the standard actually, it can be
downloaded with illustrations on the page above, but some of it in plain
(1) Pin-out Correspondence:
The following TRS to DIN drawing illustrates the wiring for a female TRS
connector in comparison to a
female MIDI-DIN connector (it is expected that devices will use female TRS
The MIDI In/Out circuitry should be implemented in accordance with the MIDI
Specification Update  (MMA/AMEI CA-033).
Because TRS connectors are often used for other (non-MIDI) purposes,
manufacturers are strongly
advised to add protection circuitry (e.g. to handle the case when a
DC-coupled headphone driver is
connected to a MIDI output).
(2) Connector Size:
2.5mm TRS connectors are recommended.
Note: If any other connector size is used, the remainder of this
specification still applies.
All cables shall use shielded twisted pairs, as defined for a MIDI cable.
The following drawing shows how to implement a male TRS to female MIDI-DIN
Adapter cables shall have a maximum length of 2 meters.
Direct connection between two TRS-equipped devices using cables designed
for use with audio
equipment is not acceptable because the wires are not twisted pair and are
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