What????? I'm not sure what you mean..... However if you are claiming there is not a way to convert from WAV to XMA, but that there is a way to convert from XMA to WAV, I don't believe you. I know it's possible to create xma files... I don't know how, and I'm hoping you or someone else might?
iv been to many sites and iv never seen the on gibbs and xentax or zenhax and thoses are the top sites for this type of info scene there was a converter to wav it seems they didn't do it the other way around