[sdiy] Caution with DIY MIDI cabling

Neil Johnson neil.johnson71 at gmail.com
Sat Dec 29 00:32:17 CET 2018


Michael E Caloroso wrote:
> I have the 1983 and the 1988 edition of the MIDI spec.  Not
> downloaded, originals from the MMA.

Excellent!  I bought a copy of the 1996 edition of the standard, way
back when the only option was to phone up the MMA with a credit card
and swallow the international phone call and postage.  This is the
same edition as that now published on the MMA website.

Looking at the detailed specification, Hardware section, 4th paragraph
in its entirety states:
"The grounding shield connector on the MIDI jacks should not be
connected to any circuit or chassis ground."

The 2014 update to the electrical specification does consider the jack
shield connection, showing that for OUT/THRU connectors the shield can
be connected to chassis, but for IN the shield must, if connected, go
through a small capacitor (e.g., 100n) to improve EMI/EMC performance.
A direct connection is not permitted.


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