I have to admit, I've always suspected there was something off about the sound in MK1 in MAME, I just couldn't put my finger on it until now.
I have a bootleg MK1 but then I don't think that'll be acceptable as a reference. The sound hardware is the same on this one but who knows if the cap, resistor values etc are. They used bootleg Yamaha and Oki chips on these too so it could sound quite different.
Is it just MK1? Surely this means all Y-Unit games sound wrong? Meaning any one of them should be an acceptable source.