[Charleston]

I just got a new Xonar U7. Then I find some problem right after I connect it with iphone compatible earbuds, which has 4 connects on its 1/8" connector. The sound becomes dumb and noisy, the volume becomes very low. But when using U7 with some nomarl stereo earbuds, it is okay.
 
Does anybody using Xonar series experienced the similar problem?
 
Thanks.
 
ps: I mean headphone socket problem, cannot correct the title after posting.