Robert Morein wrote:

Sorry, Mark, I can't agree.

The following tech sheet http://www.sanyo.com/semiconductors/news/Vol66.pdf
gives specs on the Sayn LA9251M, a common CD controller chip.
Among the features provided is
. Automatic follower operation (tracking gain and track detection level)

Because lasers wear and output decays over time, calibration to the
reflected signal at a particular point in the life in the product is
essential.

This feature is frequently referred to as AGC, and has been implemented with
varying degrees of effectivenss in different players.

For example, every Sony player I own, back to 1991, is multi-read capable,
which means that it can read a CD-RW, which of all the available blanks
differs the greatest from a pressing.

Most other brands were, at least in the past, not nearly so good. It is
remarkable that Sony built multi-read into their products long before CD-RW
was in frequent use.

My Denon I had ten years ago (bought new about 1992, IIRC) had no
problems, either. It did have an "amplified" mode so that if the
disc was reading poorly, it would basically double the sensitivity.
Another way around the problem. Never ever had it fail to read
a CD-R of any type.