Re: CD question

Dave Platt wrote:
- CD-R and CD-RW discs are inherently harder to track than a
"manufactured" (molded and aluminized) CD. The dye layer (CD-R) or
phase-change layer (CD-RW) has a lower contrast than the
molded pits on a manufactured CD. This leads to a lower signal
level as seen by the playback electronics, making it harder for the
servo to maintain position and focus on the track, and raising the
bit-error rate. If a CD player's laser is getting old and its
output level is dropping, the lower reflectivity can become a
significant problem.

I find there are two kinds of blanks available, ones that look yellow
(gold or silver) and those that look blue. Audio players, especially ones
made in the last century can not read blue disks. I think the capability
to read them came in around 2002 or so.

- "High speed" CD-R discs use a dye laser which is quite laser-
sensitive, so it can be "burned" with a short exposure...
it may have even a lower contrast than a standard CD-R's dye layer.
Vibration of the disc and drive during a fast burn can further
reduce the quality of the pits and lands, making tracking even
more difficult.

The space between sectors is well defined in the various standards. There
is a problem when you burn a CD where the data is not available when the
drive wants to write it. In the old days (1991) the drive wrote zeros in
that spot, producing a useless disk. Later the drives started detecting the
errors and producing buffer under-run errors, usually causing the burning
process to abort.

Several systems exist to prevent the errors, such as "burn free", or
"seamless link", and so on. They work by detecting the buffer under-run and
stopping the burn in such a way the disk is still readable. They still produce
what according to the original standard is an unreadable disk, but by the
extended standards they are perfectly ok.

As far as I know, CD ROM drives from around 2000, and all DVD ROM drives,
except for the very early single speed ones can read these disks without
an error, but audio players can not. Possibly the new ones with read-ahead
(anti skip) can, but most of the players out there can not.

My experience with CD-ROMs and old drives has been that if you expect to
read a disk, you have to turn off buffer underrun protection, use yellow
blanks, and record it at no faster speed than it will be read at.

DVD burners have better laser positioning, and the burn speed is less critical.

In any case, if you are not careful, you can easily burn an audio CD which
will play on a computer, and not on an audio player. Been there, done that.



I've found that a good, careful cleaning of the lower CD surface with
plastic cleaner often helps (I use the Novus brand). Usually a
clean-and-polish is enough to allow for a quick rip-and-burn. In a
few cases, I've had to use the Novus 2 scratch-remover to buff out big
scratches.

There was a thread a long time ago on the audio groups about using
Armour-All, a car polish on the disks. In every case it improved the
reading (sound) of audio CD's, but many turned cloudy after a few months.
No one knew what the long term effect was of them turning cloudy, but
that was so long ago (early 1990's) that there should be some somewhere
if one can locate them.

Dave, on a personal note, a high school friend that went to school with you
just contacted me facebook and I literally just sent him an email detailing
what was going on in my life and mentioned that you and I occasionally follow-up
each other's postings.

Geoff.


--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@xxxxxxxxxxxxx N3OWJ/4X1GM
.

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