If you are indeed using optical out from the PS3 to your receiver, it is just sending digital information directly from the CDs (ones and zeros) and the receiver is then in charge of decoding it into analog sound to send to the speakers. In other words, scratchy noises would be the last thing I expect a digital device to introduce as it 'should' just be sending the CD data directly to the receiver to be decoded.
Of course the PS3 still could be sending bad digital data but bad digital data usually results in much different sounding issues, but I guess anything is possible.
Sorry I don't have more to offer.
