Well, if we're interested in continuing this mini-thread, if you don't mind,
let me just ask this, based on my recollection of an earlier post - does
your old Sony read CD-RW discs, as opposed to CD-R discs?
Mark Z.
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"Robert Morein" wrote in message
...
I believe CD-RW is Orange Book.
"Mark D. Zacharias" wrote in message
...
I think we're at cross purposes. Red Book doesn't define CD-RW as
opposed
to
CD-R, does it?
Mark Z.
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"Robert Morein" wrote in message
...
Please read my post again.
I said that AGC is a threshold detector function. It has nothing to do
with
laser diode power calibration.
Sony players do nothing special with the laser diode. The AGC function
provides variable threshold detection, which is what gives it the
ability
to
read Orange Book.
"Mark D. Zacharias" wrote in message
...
And yet the laser power is not calibrated according to any disc
reflectivity, merely to provide a constant laser current, which is
virtually
the same regardless of whether any laser light returns from the disc
at
all.
In a multi-read model, which I will admit I have not studied, this
may
be
different. Your old Sony however, isn't multi-read in the same sense
as
a
modern CD-ROM device. It may just have the laser power turned up
somewhat.
The only unit I have seen which calibrated the laser output on
playback
was
a karaoke model - unknown Chinese vendor. Viewing the HF pattern on
a
'scope
one could observe the laser "eye pattern" ramping up depending on
the
disc
type. Your Sony does not do this.
Mark Z.
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"Robert Morein" wrote in message
...
"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.