[sdiy] MIDI optoisolator candidates?

[Colin f]

> The value of the output resistor makes a difference 
> to the quality of the midi output, as well. I think.

Absolutely.
I had great trouble finding the right values of output resistor to get a
MIDI input stage that would work reliably.
My problem was partly caused by a book I got years ago which gave examples
of different opto-isolators that could be used for MIDI input, all with
poorly chosen resistor values that don't work reliably.
I assumed for years that I must be doing something else wrong other than
simply believing an R.A. Penfold schematic...
Now I either use a 6N137 or 6N139, both with a 470R or 510R load resistor.
6N139 draws slightly less supply current, which can be useful if you are
retrofitting MIDI in an old synth with a very ropey power supply.

Cheers,
Colin f