try swapping the left and the right rca plugs on the cdp output, if the distorted channel swaps place then it's the cdp, if it doesn't then somewhere along your audio chain is the culprit, check your interconnects. check your media too if it's a burned audio cd.
if you think it's the cdp, check again if it has a headphone jack infront and plug a headphone and listen if the sound in one channel is distorted. if not then your problem is in the output section of the cdp which can be caused by a multitude of parts, heck, it can even be caused by a bad muting transistor.