In my case, I have AvsP inside my Dedicated 2-slot MVS cabinet (which has a 6-slot in currently) and you simply WILL NOT get audio from the MVS(fake jamma?) connector in my dedicated MVS cab...
The only way I can get audio is via the RCA jacks to the mixer/dj setup on the other side of the room. Also, if the CPS2 board set is set to Q sound, even with the RCS jacks connected - no sound. It HAS to be mono in order to put out sound through the RCA jacks....
God only knows why. And this is simply my own experience with this game here - so your mileage may vary.