I’m trying to wire build a Jamma arcade cabinet from scratch. I have a question on how to properly wire audio. The Jamma standard have two pins related to audio (+/-). I have connected + to a phobo plug middle and - to the phono shield. The phono is connected to my OSSC upscaler via a phono to jack adapter. This setup causes weird behavior and restarts.
If I just connect the middle and leave the - disconnected everything seems to work ok. I suspect this only works because the devices share a common ground in the power supply. I want to make a system where I also have the option to connect my home theater amp, so the outer jacket needs to be terminated properly.
Have access to both Neo Geo and CPS/CPS2 jamma games. Problem applies to all of them.
Any suggestions/real knowhow on how this is supposed to be wired? Should the jamma - pin be left out and connect the outer phono jacket to ground instead? Do I need to add any components like resistors or similar?