"Mark D. Zacharias" wrote in message
...
I was talking CD-R, not RW, haven't tried those in the older Sony's but I
would be surprised. Lots of other units use the Sony pickups, and none of
them boost the laser power based on reflectivity - a constant current is
maintained as a voltage drop across a resistor, indicating a constant
laser
diode current, regardless of reflected signal received back to the diode
pack. The APC (not ACG) transistor is mainly a switch, though as I say the
current is kept nearly constant.

Mark Z.

I did not intend to imply that AGC is an adjustment of the laser diode.
It is an adjustment of the threshold detector.



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"Robert Morein" wrote in message
...
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.

I have the service manual for all my players, and none of these older,
multiread capable units have either a calibration pot or a service mode.



"Mark D. Zacharias" wrote in message
...
With VERY few exceptions, audio CD players do not calibrate laser
power
automatically. Some are adjusted with physical potentiometers, some
newer
ones do it in a service mode using eeproms, but once set, the laser
calibration is done.
Focus is adjusted dynamically while playing, and of course during the
focus
search routine. Focus offset value is kept in memory until the next
disc
read operation so that if the PLAY button is pressed again, it can
spin
immediately without doing another focus search.


Mark Z.

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"Robert Morein" wrote in message
...

"Surinder Singh" wrote in message
...
I play the CD's I burn in Phillipps Boombox. If I Maxell Gold CD-R
it
takes
20 seconds for the boom box to recognize the tracks and be ready
to
play
it
after inserting the CD. With Memorex 52x, it takes only 2 seconds
for
boom
to recognize the tracks. Does it mean that Memorex is better
quality?
I
would have thought the gold coloration ;-) & Maxell name would
make
the
former a better quality?

Thanks.

Different CD disks have different reflectivities for the burn/no
burn
conditions.
The CD player has a calibration function that enables it to
correctly
recognize these conditions.
Depending upon the design of the player, the ability to recognize
disks
with
different reflectivities vary.

Only a few years ago, it was common for many brands of CD players to
fail
to
recognize CD-Rs, because insufficient range had been built into the
calibration function.

What you observe has more to do with the player than the disk.
Gold as a reflective material has a signficant advantage for
archival
use.
However, it is somewhat less reflective than aluminum.