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

[Andrei Kudryavtsev]

Speaking of TRS mess, found this one in the recent application list for
MIDI innovations:
https://midi.org/innovation-award/psimidi

On Thu, Jun 27, 2024 at 7:54 AM Martin Klang via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Well the input, if MIDI compliant, is protected by an optocoupler.
> Shouldn't that be enough?
>
> I've seen plenty of DIY and not-so DIY circuits where the output comes
> straight off an MCU pin, which makes it susceptible to over-voltage and
> current. I'd put a transistor in line at least.
>
>
>
> Martin
>
>
>
> -----Original message-----
> *From:* Mattias Rickardsson <mr at analogue.org>
> *Sent:* Thursday, June 27 2024, 4:29 pm
> *To:* grant musictechnologiesgroup.com <grant at musictechnologiesgroup.com>
> *Cc:* synth-diy at synth-diy.org <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] MIDI cable impedance and MIDI In ESD protection?
>
> <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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-- 
Andrei Kudryavtsev,
Deftaudio www.deftaudio.com
Manufacturing Luma-1 Drum Machine
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