The CD system - the engineering reality
Er, no! Have you allowed your preconviction that 'CD players sound different' combined with your abandoned belief that 'DACs sound different' to grasp for a second belief that 'the all important element is the CD mechanism' (I summarise).
Originally Posted by Diminish
There may well be sonic differences between CD players - I'm not listening for them but I don't doubt that something is audible - but you are barking up the wrong tree if you think the CD mechanism is complex and hence, likely to be the source of any differences. The miracle of the CD concept (as I've discussed long ago) is not its complexity but its extreme electro-mechanical simplicity. I repeat - the Sony/Philips designers intentionally, deliberately and wholeheartedly approached the design of the discs and the players with cost minimisation (aka engineering simplicity) at the very top of the design specification. And were they proved right: absolutely. It was a wonderful collaborative effort between European and Japanese engineers who shared different cultural approaches to engineering perfection, but found a solid common ground.
The reason is this: driven (rightly) in the early 1980s by marketing predictions of the likely consumer uptake of audio CDs (billions of discs, tens or hundreds of millions of CD player mechanisms), combined with the persistent and costly returns of mis-pressed LP records by the public, the engineers wanted a completely foolproof 'sell and forget' system. Discs that were (are) cheap to duplicate, indestructible, almost totally immune to even severe scratching and with player mechanisms that would cope with anything thrown at them. And that translated in the engineering design to the CD system's ability to cope with a huge spread of manufacturing tolerances in the discs and mechanism plus likely consumer/environmental degradation (another set of wide tolerances). So they anticipated every imaginable scenario of player and disc edge-of-tolerance: just a little bit too fast or too slow, a fresh laser or a weak one after years of use, dust on the laser, rotational bearing wear leading to non-concentric rotation, bearing oil/grease becoming sticky, laser misalignment laterally and vertically, scratches along and across the disc, disc data pits with fuzzy not sharp edges, flaking reflective CD top layer, likely power supply variation country to country, hour to hour etc. etc. etc.. In microcosm, they 'put a man on the moon and brought him back'.
And what did they conclude? They appreciated that the entire CD player/disc system had to have built-in significant error correction and feedback systems, mechanically and electrically. And these systems themselves had to be robust and reliable, fast acting, completely transparent to the user, automatic, and that the user could not even if he wanted to, 'go manual' and bypass layers upon layers of complex interlinked self-regulating feedback control systems. And that was a genius decision. There could be no tweaking of the transport, no re-writing of the control code, no user controls other than basic play/stop/search and no possibility at all to reinterpret, reinvent or improve upon the transport system devised by the collective genius of the worlds best consumer electronics working across two continents. And that's how it stands today.
And the consequence of superb engineering foresight was that both the discs themselves and the transport mechanisms could be punched out in sweatshop conditions without the need for a super-clean environment, using simple machinery in the hundreds of millions. No need to tweak and adjust every mechanism. Just bash them out and flog them in vast quantities. And that ensured (as Sony/Philips anticipated) that the cost of producing the mechanism would fall to little more than the cost of producing the disc, wholly unlike the LP record and its player mechanism.
Attached is a scan from a current (and rather pricey) trade catalogue listing CD and DVD players for the PC. They sell the mechanism in a tin case to suit a PC, in a nice cardboard box with instructions, screws, audio cable etc.. Item B, cost GBP 12.95 will have a mechanism that is functionally identical to what you'll find in an audio CD system (plus lots of additional features incl. Lightscribe, ability to read and write up to 48x - CD audio is only 1 x). Item D can read BlueRay which is a far, far more complex disk to read and interpret than CD audio. It's cost, GBP 42.95. From this I suppose we can assume that the cost of the mechanism itself, made in China, can be no more than a few dollars.
And as for 'jitter'; the implications of that certain inevitability was fully considered by the Sony/Philips designers who built-in perfectly adequate and completely robust correction systems to guarantee that it just would not be an issue at all for the consumer.
Alan A. Shaw
Harbeth Audio UK