Hi!
Im just wondering is it correct, the proper way, to make extra MIDI-THRU ports just connecting them parallel to exist MIDI-IN ports.
Or will I face some problems in future?
It’s like splitting MIDI-cable for several MIDI-INs.
I have this one device where I need couple MIDI-THRU ports.
cheers, cAMEL
You can’t make MIDI Thru by connecting them directly in parallel to MIDI In ports… The MIDI hardware is a current loop - when connecting MIDI Out to a MIDI In, current goes from the MIDI Out, through the optocoupler connected to MIDI In, then back to the MIDI Out. Splitting this would result in less current going through each MIDI In, which might not be enough to drive the optocoupler properly.
See a schematic of how it should be done here:
http://m.bareille.free.fr/midithrubox/midithrubox.htm
I have made a “hack” MIDI Thru port on a Core by connecting the optocoupler output to a standard MIDI Out socket
i.e.
DIN socket pin 4 -> 220R resistor -> 5V
and
DIN socket pin 5 -> 220R resistor -> optocoupler output (Core IC2:pin 6)
It works, but it will only work for one MIDI Thru port, maybe two, I don’t know… the “right” way is to use buffers (see the schmitt trigger inverters in the schematic - two of them invert the optocoupler output twice, so it’s the same, but “buffered”).