Theoretical question about how CD's work

There are quite a few reasons why the same issue CD of a recording from different CD manufacturing plants sound different on the same CD player.

The accuracy of the process of laying down the bits and lands on the metal master.

The accuracy of producing the actual CDs from the metal master. The edges/transitions between pits and lands must be perfectly clean and correct with respect to timing (lengths of pits and lengths of lands).

Differences in the inks used for the CD label. Some inks may be more ferrous. Also if the colors of the inks are different that would influence the sound, too.

The thickness of the CD can influence the sound since a thicker CD will be stiffer and not flutter as much during play as a thinner one.

The transparency/purity of the polycarbonate layer. The nominal transparency of polycarbonate is actually only about 91%. SHM-CDs employ a more transparent material for the clear layer. Hence Super High-performance Material (SHM). Less transparency, more laser light scattering.

The purity and composition of the metal layer. Some metals and alloys have higher reflectivity for infrared light than others.

The variation in roundness of the CD. We know that out-of-round CDs flutter and flop around more than CDs that are perfectly round, causing mis-tracking.

OK so I learned something. Analog means distance and speed dependent. I am off this thread . . .

Have you flipper your gizzard? Nobody said CDs are like Laserdiscs. I already explained why laser reading is an analog process. That doesn’t mean the transitions from pits to lands and lands to pits don’t represent 1s and 0s. But those 1s and 0s represented by the transitions do not (rpt not) represent the music signal (waveform).

The laser reading of the transitions is an analog process. The laser reads, ON, OFF, ON, OFF according to whether the photodetector receives a reflected signal or no signal. The transitions occur between ONs and OFFs. And the system keeps track of the time periods between transitions. So, the lengths of pits and lands is also important in organizing the transitions into meaningful data strings, according to the Redbook standard.

The “1s and 0s” detected by the photodetector have to be decoded into predetermined strings of meaningful data downstream. As the link I provided a couple weeks ago shows there are approximately 9 or so discreet strings of data that are read off the Compact Disc. The 1s and 0s represented by transitions don’t mean anything until they’re organized even when they’re organized they still don’t mean anything until they go through a Digital to Analog Converter DAC. But, unfortunately, as I’ve stated many times, by the time the organized 1s and 0s get to the DAC it’s too late to recover from all the damage to the original data on the CD. The reasons for the damage include,

1. Scattered laser light that above a certain energy level gets into the photodetector and is interpreted as real signal. Since the laser is invisible infrared 780 nm attempts to block scattered light with green pens is only fractionally successful. There is a red component to the CD laser for safety reasons. It’s that red component of the scattered light that green pens absorb.

2. Mistracking of the laser caused by external vibration as well as vibration of the Compact Disc itself while spinning. The fluttering and wobbling is caused by out of round discs and exacerbated by the non level spinning of the disc. Mistracking occurs even though Reed Solomon Error detection/correction codes supposedly correct all errors and even though the laser tracking servo system supposedly keeps the laser on the data spiral at all times.