Necromancing an old thread.. I just took a quick look at the PGM audio and potential stereo mod. But as people have pointed out, there's no stereo audio in the games and there's also no multichannel synth business for stereo modding like eg. an NES, so barring actual stereo sound, remaining benefits for the "stereo" output mod are:
- Separate and independent. JAMMA edge continues to function as-is.
- Line level and clean. No accidents involving the PCB volume knob, and more importantly coupling caps for cleaning up noise-causing DC components from the audio.
- Properly impedance matched. Only misguided "audiophiles" care about this one, though. Audio quality on arcade gear in general is so bad, you'll need a rich imagination for this to make any difference.
- 2x RCA connectors, or whatever you choose. If you want the audio going somewhere else than a supergun or a cab, 2x RCA is usually most convenient (also for mono audio, since what you actually want is probably 2x mono).
- If some day people actually do produce stereo-modded games and put them on carts, you'll be ready. Linux users in particular are likely to get hard over this one.
Since PGM has a suitable opamp to tap to, it doesn't need a separate line driver and it can also be used to drive consumer headphones.
Felt like I needed to write this, since googling for PGM stereo mod produced so many profoundly unhelpful "no benefit whatsoever" responses...
Not that this post is actually very helpful, either. I quickly tested things to see how it works, but not yet built any proper prototypes or even decided on the design. Sorry!