Many of Julian Dunn's classic AES papers on jitter can be found here, and are IMO required reading on the subject:
http://www.nanophon.com/audio/
Two big conceptual errors I see very commonly are the assumption that any intrinsic jitter related to retrieval of information off of a CD actually occurs through the forward signal/data path, and that any sonic artifact associated with parts upstream of the DAC must be classifiable as jitter.
In reality, CD players, transports, and DACs are a menagerie of true mixed-signal design problems, and there are a lot of different noises sources living in close proximity with suceptible circuit nodes. One oft-overlooked source is crosstalk from the disc servomechanism into other parts of the machine . . . analog circuitry, S/PDIF transmitters, PLL clock, etc., which can be dependent on the condition of the disc.
One easy way of measuring this on the test bench is to have two versions of the same test-tone CD, one pristene, the other scratched. A conventional distortion analyzer is used to null out the the tone(s), and then an FFT (or visual 'scope analysis) is used to analyze the residual. One would be suprised at some of the nasty things that sometimes come up out of the noise floor when the focus and tracking servos suddenly have to work really hard to read the disc.
But that said, demagnetizing a CD is of course silly. If it's scratched or hazy, I use a 3M product called "Finesse-It", which is sold as a professional polishing compound for automotive finishes. Sometimes spot pre-treatment with a Mr. Clean Magic eraser on particularly tough scratches helps, then Finesse-It to remove the scratches left by the eraser.
http://www.nanophon.com/audio/
Two big conceptual errors I see very commonly are the assumption that any intrinsic jitter related to retrieval of information off of a CD actually occurs through the forward signal/data path, and that any sonic artifact associated with parts upstream of the DAC must be classifiable as jitter.
In reality, CD players, transports, and DACs are a menagerie of true mixed-signal design problems, and there are a lot of different noises sources living in close proximity with suceptible circuit nodes. One oft-overlooked source is crosstalk from the disc servomechanism into other parts of the machine . . . analog circuitry, S/PDIF transmitters, PLL clock, etc., which can be dependent on the condition of the disc.
One easy way of measuring this on the test bench is to have two versions of the same test-tone CD, one pristene, the other scratched. A conventional distortion analyzer is used to null out the the tone(s), and then an FFT (or visual 'scope analysis) is used to analyze the residual. One would be suprised at some of the nasty things that sometimes come up out of the noise floor when the focus and tracking servos suddenly have to work really hard to read the disc.
But that said, demagnetizing a CD is of course silly. If it's scratched or hazy, I use a 3M product called "Finesse-It", which is sold as a professional polishing compound for automotive finishes. Sometimes spot pre-treatment with a Mr. Clean Magic eraser on particularly tough scratches helps, then Finesse-It to remove the scratches left by the eraser.
