I know this is an old thread but I thought I'd try and see if any of you have a suggestion. In the past, I never had any luck with a stereo 1/8" patch cable and the only way I was able to pass the IR from the C4 controller to an HDBaseT sender (using the Accell units - https://www.amazon.com/Accell-E090C-003B-UltraCat-Single-Extender/dp/B0058M3RW8/ref=cm_cr_arp_d_product_top?ie=UTF8) was to attach an emitter to the EA5 output and then attach an IR receiver to the HDBaseT sender. I tape the two together and it has worked reliably but always to be a hack.
I am updating some things in my rack and thought it would be nice to clean those up but I haven't been able to figure out a way to from the C4 mono IR output to what I assume is a stereo IR input on the Accell units. I've tried a mono to stereo adapter and a binary 12V adapter that says it "removes 12VDC for IR connection to control system" with no luck.
Any ideas?