I made this MIDI to CV box and for years it worked just fine receiving MIDI from my computer's M4UXL USB controlled 4 in / 4 out MIDI box. Then I decided to go back to my roots and use my Atari and the damn thing doesn't work with it, every fourth or fifth MIDI note seems to get through but the rest don't. I'm guessing this is something to do with the way I wired the MIDI input, I used an opto isolator and left the shield ground unconnected at the input as per the MIDI spec.
Any ideas why it would work for one MIDI generating device but not another?