Most music CD's are heavily compressed and peak at digital 0dB. Because we are porting the USB stick directly into a channel, we can attenuate it (if it's really too loud) but we can't adjust the incoming gain. Your CD music should sound fine; it's merely tripping the clip indicators. To solve this, you can edit your WAV file in an audio editing program and drop its gain a few dB. This will stop the clip indicators without harming the sound quality of your files.