just tried mk2 and 3 in lr-imame4all – both have occasional distortion for me. happens a few screens into the intro for me on 2, for example. can’t access service menu (what button?), and RGUI audio volume option doesn’t seem to do anything. it’s strange – doesn’t seems consistent like the audio is clipping, just just occasionally for no real reason.
repeated the experiment in lr-mame2003. mk2 seems perfect (no distortion or slowdown), and same story with mk3, i’m sure both of these games had slowdown/distortion last time i tested! but yeah, ok 🙂
bizarrely, mk1 does have sound issues on lr-mame2003 for me, though. it’s a lot louder thank 2/3, but it has almost constant distortion. tab gets to service menu but i don’t see any audio options.