So how would you wire a single set of speakers to work with both mono edge connector audio and the additional stereo output?
I'm about to do this with my Ikari Warriors cabinet.
It currently has only 1 speaker, wired per the JAMMA standard (amplified mono audio on L/10 of the harness). I currently have an ArcadeSD board in there, which outputs the JAMMA-standard mono on the harness, but also supports (will support?) unamplified stereo via a seperate 4-pin connector. I plan to add a 2nd speaker, an amplifier, and re-wire to support either situation.
Of course, I'll need a stereo amp that can output a few watts into 8 ohms. I'll also have a connector in the cabinet which terminates the speakers (4-pin, + & - for both speakers). That'll plug into either:
(a) a connector which jumpers the L & R speakers, and then connects that to the JAMMA L/10 pins, effectively putting the two speakers in parallel, and presenting a 4ohm load to the PCB amp.
or
(b) the stereo output of an amplifier, which is in turn connected to the 4-pin header on the ArcadeSD PCB. This will, of course, provide an 8 ohm load to each channel of the amp.
My arrangement is an either/or. I'll need to physically unplug the speakers from one connector and into the other in order to change the audio source. I don't know how to do it any other way... diodes won't work, like it can with controls, as audio is an AC signal. I don't think it's advisable to connect multiple amplified sources to the same speaker(s) at the same time...