ive played hundreds of cds, and it does it too when i play the regular radio

 

My JVC has a little bit of hiss when I play a CD. I think it is just the sound interference coming from the unit itself being amplified. Quiet passages, and the dead space between tracks is when I notice it. It does not do it when playing from the XM or the radio. In fact, the hiss I hear has a rythmic quility to it that could be construed as the optical pickup for the CD. In fact, I am sure of it. I never noticed it in my Teg because I didn't have an amp, but in the CL, the amps magnify that signal noise. That is probably your issue as well.

Good luck.

P.s.
If it were a ground issue, you would have problems with the radio as well as the CD.

 

i think if it is the ground problem the power would go in and out, hu would dim and undim. try pulling ur HU out and wrap a thick layer of electrical tape around the the yellow wired. could be a EMI issue.