ESD, was : RE: [sdiy] midi optocoupler isolation voltage?

[Neil Johnson]

> I *think* that the two wire midi bus is shielded via copper mesh, that
> should be connected to the "ring" of the midi/DIN cable.
> Both devices should connect chassis ground to that. So no potential
> difference can build up between two pieces of midi gear in terms of DC.

*Ack* no!  From the MIDI 1.0 Specification:

"The grounding shield connector on the MIDI jacks should not be connected
to any circuit or chassis ground."

Also, regarding connection to the shield:

"Pin 2 of the MIDI In connector should also be left unconnected."

In essence there must be _no_ electrical connection between the MIDI jacks
of any two devices, otherwise you'll have an earth loop (Bad Karma).

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
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