[sdiy] Midi opto isolation

[paul.maddox.mail-list at synth.net]

Sean,

> Over the years I have picked up some modules that have trouble with
> complex
> midi signals. I'm considering ways to fix them like improving the midi
> inputs stage but I'm curious, why have the signal isolated? Surely using
> the
> isolation lowers the quality of the signal with very little benefit, is it
> really needed?

couple of reasons

1) Midi is a current loop, not voltage
2) Noise/ground issues.

in theory using the isolation doesn't reduce the quality of the signal, in
fact it can be quite the reverse, with a nice snappy opto-isolator device
you can really clean up the edges of a transmission.

Paul