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

[Richard Wentk]

At 20:19 10/03/2003 +0000, Neil Johnson wrote:

>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).

Worse than bad karma. You can get MIDI clicks coupling through to your 
audio. Play a note, get a click. Move your mod wheel, get a ripping noise. 
Very not good.

The whole point of the MIDI spec was to make sure that stray voltages from 
lightning strikes, insane roadies on drugs connecting your MIDI line to 
mains, and EMP from a nearby nuclear war would never affect the reliability 
of your MIDI messages.

The opto is there to make sure the two synths are as disconnected as 
possible, while still being able to pass information to each other. 
Connecting them directly violates the Disconnection Principle, and is most 
definitely bad.

Richard