Hey, I don’t know how the A4 works, but if it works like the MD you may not need a thru-box.
In my setup, I have :
- OT as master clock going to MD
- then MD MIDI OUT goes to some synth
- MD MIDI THRU goes another synth
When slaved, the MD still sends MIDI clock info on its MIDI OUT, and copy the MIDI IN (from OT) to its MIDI THRU. This way, you get two clock outputs on one machine. Neat.
Maybe try and see whether the A4 could do the same?