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-----Original Message-----
From Tom Fine: "Is there any science on whether jitter from a CD drive can
audibly effect a "rip" of that CD to MP3 or other lossy-compressed formats?
"

If everything is working properly, the data is replicated perfectly. If not,
it's more likely to be a train wreck or at least clicks and pops as opposed
to analog-sounding issues. Jitter in a CD is very different from interface
jitter in an audio stream which can in some designs corrupt  the D to A
clock. My understanding is that its effect is making the disk harder to
read. That could, depending on the particular player design, create a very
slight overall speed change caused by the effect of increased servo
activity.

All of this is about the effect that  the analog circuitry that handles the
data has on the D to A and power supply. This can include corruption of the
clock caused by rfi and changes in the temperature of the crystals that are
caused by changes in the amount of current used by the motors and servo
system. The better isolated the D to A is from the transport system, the
less effect there should be. Different designs obviously offer different
levels of actual isolation.

I attended a fascinating rollout of HDTV by the SMPTE in San Francisco. It
turned out that it took a couple generations of digital video production
gear for the designers to learn how to eliminate jitter problems in a
television studio. They had hired some top digital audio engineers to
develop their original interfaces. Unfortunately they couldn't tell a
director who was pointing at an artifact on their monitor and demanding to
know "what the !@#$ is THAT?" to go take an ABX test. While the design of
jitter-free interfaces has been known science for decades, it somehow never
made it into the first several generations of digital audio and video
interfaces. What was learned in video apparently has finally trickled down
to audio.

Unfortunately anything that causes a change in sound when people mistakenly
believe that it shouldn't leads to both pontificating by ABX fundamentalists
and audiophile fantasies that totally misread what it is that changed or the
cause. In digital audio, only the data is digital while everything that
handles both the data and the audio signal is  very much analog and subject
to all of the problems of analog electronics. Unfortunately there has been a
lot of incompetent digital audio equipment and chip design that has caused a
great deal of confusion.


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