I just love emulation 
I’ve made a few myself (with collaborators), probably most notably JEmu2. It emulates lots of arcade games (up to games like Galaxy Force 2, Rail Chase, After Burner and Outrun), and a few consoles and home computers (Sega Master System, MSX, MSX2, Spectrum) and it supports sound.
A few questions though:
Any reason why you’re porting such an old MAME release? Is it because later releases started to depend on macros and such so much?
And why a direct port? I haven’t looked at your code yet, but I found that following MAME to the letter will make the code very rigid and ‘static’. In JEmu2 I would never have been able to implement things like ‘VirtuArcade’ (i.e. 20 arcades running in parallel in 3D) if JEmu2 was a straight MAME port.
If I were to write an emulator again, I’d not follow MAME too closely but just make some helper classes to make porting MAME drivers easier. MAME is a beautiful piece of code that despite its age is still quite well designed and is an invaluable treasure of knowledge. But IMHO it doesn’t translate that well into java, especially if you want to take emulators further than MAME.
Anyway, I’ll check out your project and see if I can merge some of my sound code in there.