Once upon a time on usenet ~misfit~ wrote:
Once upon a time on usenet Phil Allison wrote:
~misfit~ wrote:

----------------------


CD-RWs required more sensitive optics on the part of the playback
device, CD-Rs however once they were written with PCM audio data
(_not_ mp3 files) and finalized IIRC were essentially the material
equivalent of a commercial Red Book audio CD and should work on any
CD player, even ones from the 1980s.

Actually CDRs are much less reflective than 'pressed' CDs and as
such some older CD players don't have the laser power needed to get
a good (reflected) signal.


** CDRs use the same metallised ( Gold or Silver) reflecting layer as
a normal CD.

Yes. The difference is in the construction of the non-refecting
areas. In a CD they're pressed into the refecting later

layer not later.

and become
'pits' whereas with a CDR a dye layer between the reflecting area and
the pickup laser is 'burned' changing it's reflectivity index.

I forgot to mention that this dye layer that is burned into a non-reflective
bit when a CDR is burned is not as optically clear in its unburned state as
the clear coat on a pressed CD which results in a lower index of reflection.
That when combined with the following results in CDRs being harder to read
than pressed CDs.

The
result, done on a modern high-quality burner on a modern high quality
blank and at a reasonable speed is close to a pressed CD w/r/t
readability. However a lot of CDRs are burned too fast and / or are
not top quality blanks resulting in a less-well defined change from
reflective to non-reflective which can give some older readers
problems. Especially when they were first on the market.
It's not so much of an issue these days as the quality of blanks has
improved considerably and the price of good quality ones has come
down. There used to be a large difference in price between the
cheapest discs and the best discs and and a corresponding difference
in readability. This could give some older players - especially those
with lasers that were starting to weaken - issues reading CDRs.

They play perfectly in my 1982, Sony CDP101.

My 1986 Philips CD 160 and my 1987 Sony CDP-17F will both read all of
my newer CDRs but used to struggle with ones I burned in the early
days when discs and burners weren't as good. I still have some of
those CDrs and even though they've been looked after and are in good
physical condition both of the older players struggle with them.

I don't have an older player any longer and will probably be getting
rid of those two soon as them not having remotes and me having
mobility issues makes it so I hardly use them these days anyway.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)