[sdiy] MIDI cable impedance and MIDI In ESD protection?

Mattias Rickardsson mr at analogue.org
Thu Jun 27 16:17:50 CEST 2024


<grant at musictechnologiesgroup.com> wrote:

> The latest MIDI electrical spec CA33 shows "optional ferrite beads to
>  improve EMI/EMC performance (FBx 1K @100MHz)"as well as "optional small  capacitor
> (0.1 μF typical) to improve RF grounding", along with diagrams.
>

And I realize that the TRS MIDI spec (RP-054 from 2017-18) writes an
unspecific answer to my other question:

"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)."

In the world of massive Eurorack systems and tiny plastic synths I expect
that pretty loud signals are sometimes connected to MIDI Ins & Outs when
confusing TRS MIDI with audio cables. But I wonder what the MMA would
suggest that this protection is made, not only in the output case that they
mention as example. :-)

/mr
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