Author Topic: DIrectly linking two MIDI circuits without opto isolator  (Read 640 times)

Mick Bailey

DIrectly linking two MIDI circuits without opto isolator
« on: January 15, 2022, 07:37:26 AM »
I want to feed the MIDI out from one circuit to the MIDI in of another. The two circuits are the EPE guitar to MIDI and the other the Obsolete Technology MIDI to CV/gate circuit and these would be built on the same board. Given that both circuits will be sharing a common PSU, can the two be directly connected without the need for the opto isolator? I was thinking that maybe just the two current limiting resistors on the MIDI out would be necessary.

EPE magazine PDF here with schematic https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiy2amb4rP1AhVVgFwKHbx9CAUQFnoECAMQAQ&url=http%3A%2F%2Fcache.amobbs.com%2Fbbs_upload782111%2Ffiles_23%2Fourdev_512212.pdf&usg=AOvVaw31KDqidbSrryuaig9S6grF 

Obsolete Technology schematic https://obsoletetechnology.wordpress.com/projects/midi-cvgate-converter/

Digital Larry

Re: DIrectly linking two MIDI circuits without opto isolator
« Reply #1 on: January 15, 2022, 10:36:38 AM »
Totally makes sense.  The isolator is just to prevent ground loops.  It's just a logic signal.  No need for current limiting.
« Last Edit: January 15, 2022, 03:45:09 PM by Digital Larry »
Digital Larry
Want to quickly design your own effects patches for the Spin FV-1 DSP chip?
https://github.com/HolyCityAudio/SpinCAD-Designer