The CD unit itself is the exact same on the US Turbo Duo and the JP Duo, DuoR, and DuoRX.
Regarding the CD unit and swapping it. A new CD unit definitely seems to improve shoddy audio, but it won't solve the problem. I still can't isolate what circuit is shitty on these things and it's driving me nuts. I even figured out which circuit is responsible for the "speech synthesis" in the games and got replacement parts for that, but that's only a problem in very very rare cases (found one actually).