-----Original Message----- From Jerry Hartke: "...Long ago, differences from listening tests were surprisingly traced to subtle differences such as disc unbalance, tangential variation of reflectance, and radial tracking (push-pull). " This is more specific information than I had learned about previously. As I posted before, according to a Philips engineer these factors can change the temperature of the crystal that the DAC is locked to in many common CD player designs. He said with some players even the silkscreen design and color can change the playback speed. As far as I know error correction has no audible effect and the disk's construction is only a factor to the degree it also happens to affect the above mechanical factors. Bob Olhsson Audio Mastery, Nashville TN Mastering, Audio for Picture, Mix Evaluation and Quality Control Over 40 years making people sound better than they ever imagined! 615.562.4346 http://www.bobolhsson.com http://audiomastery.com