But that noise and vibration mean absolutely nothing in terms of the signal coming out.
Noise and vibration are not really problems inside a normal CD player.
On the contrary, Brett and Turkey, there are many articles on the sources of signal degradation that finally come out of a DAC. Noise and vibration from motors and actuators and timing variations all contribute to jitter, a concept some just don't believe in, even though the literature is overwhelming. Enter keywords "CD jitter."
Thanks for that little lecture, but I have worked with stuff like this all my professional life, so I am pretty well up on how to do it. This is really not much more than 70's TTL logic and as a matter of fact, in terms of reading digital data and converting it to an analog signal, it works virtually identically to a satellite control system* that I used to work on that was designed in 1968.
Jitter is only a problem when you design the DAC incorrectly, i.e. "whenever the word is read, I will switch the input to the A/D output" vice 'I will switch the input of the A/D to the next word on the leading edge of my 44.1 khz clock". If you do the latter, it's a no-brainer, the jitter by definition NEVER gets to the output, there can be no argument.
I don't have to "believe" in anything. That's the nice thing about science, mathematics, and engineering, it gives definitive answers. I would also note that the vast majority of the "audio" world is arranged more along the lines of reading goat entrails, astrology, or "The Sting" than engineering principles. So I have no doubt that you can get all the disc dampers, green magic markers, and magic good-sounding bricks for CD players that you want, and endless purple prose about why you need it. I mean, there are still idiots buying $3000 interconnect cables - if you can convince people on that, they are ripe for the plucking.
I would also argue that the relative effect of any magnitude of jitter arising from the former method. You get this tiny timing variation from word to word, then run the output through a very sharp-cutting filter with a bandpass of about half the bit rate. That alone greatly washes out any timing variation. But at least you could argue that - you can't argue the first.
The only legitimate point you could possibly have is RF noise coming out of the box - but that has nothing to do with jitter or the bits that are retrieved from the disc, which was what we were discussing.
Brett
*DSCS II satellite, a box called the Despin Electronics Assembly, took a digital word from an Earth sensor up/down counter, waited for a clock leading edge, converted it to an analog voltage by applying it to an D/A converter, that then ran the resulting through an PID control system (an amplifier with some intentionally reactive elements) that resulted in an analog torque signal to a motor that turned a despun antenna platform. The essential elements are identical - so it's not like reading the bits off a CD is some new hard problem to solve, In fact it was common knowledge back in 1968.
