Can CD Players be altered to play CD-Rs

The reason CD players cannot read CD-R's is that their lasers are not tuned to the wavelengths of the light that CD-R's reflect, or that the laser pickup isn't sensitive enough (CD-R's don't reflect very much). So without changing out the transport, I'd say no

I was under the impression that the inability to play computer CD-R's or RW's was the fault of the transport's optics. CD-R aren't as reflective as reglar CDs. And CD-RWs are much worse, from what I've been lead to believe.

You could try experimenting with different colors of film. sometime you have better luck with green, blue, gold, etc whatever color in a particular transport.

Athough, the above should read some CD players won't play CDR's. Many will, ie my 13 year old Magnavox cd630 and present Rega Planet. Of course there are many more that do to!

Some CD players will play CD-Rs. There are several
variables to consider.
First and foremost, I make back-up copies of some of
my CDs and they play just great in my Corvette's CD player;
as well as my two home players - a two year old Teac in
my bedroom system and a soon to be traded Cyrus Mission
player in my main system.
I record my discs on a commercial grade CD recorder -
a Marantz CDR500 - in real time. I also use top of the line
CD-R discs - usually high end discs from Imation, Sony, or
TDK. I NEVER use those cheapie "bulk" type discs - the 50
for $25.00 ones. They are all junk!
I would be willing to bet that any CD-Rs that don't
seem to play in a conventional CD player have at least one
of the following traits: 1) Were recorded on a computer
CD-R drive. 2) Were recorded at a speed two or more times
faster than play speed. 3) Were recorded on cheapie discs.
4) Recorded on a heavily used CD-R drive that has never
been cleaned.
Hope these hints are of some help. By the way - some
of the lower end commercial CD-R recorders are only a few
hundred bucks more than most consumer models, ignore the
SCMS copy code, and usually have better build and warranties.

I agree w/Avideo. I have an old Denon CD changer in my system that plays CD-R's. I copied Jazz at the pawnshop CD on my computer's cd burner. When I A B them the copy sounds terrible.

FWIW, I just bought a Pioneer PDR-05 (used). It copies in real time and the copies play just fine on my CAL CL-10, my Eclipse unit in the car, my wife's Acura unit, my son's Sony walkman and his boom box. I have to use the CDR-Audio disks and I bought Sony, but have NO problems.