WorldJAZZ wrote:

"Codifus" wrote in message
et...

Mark D. Zacharias wrote:


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.


If your CD player can read a CDRW, then it's got quite strong laser
beam.


It is not a question of beam strength.
Photodetectors can be incredibly sensitive, far more than required to sense
the reflection from a CD of any type.

The problem for the designer is to determine what level of reflectivity is
equivalent to a transition, and what level is the base reflectivity level.

This requires what is commonly referred to as an AGC circuit, though it may
go by different names. It determines the threshold that applies to the
particular disk.

Although this is a simple circuit, designers originally made AGC circuits
that could accomodate the range of various CD pressings. As the available
types of media diversified, AGC circuits were required to function over a
wider range.

Exhibiting an unusual degree of foresight, Sony CD players were equipped
with AGC circuits capable of handling media that would not be in common use
for years. Other manufacturers, particularly Panasonic, lagged developments
in media.


Nice. I wish my old Sony player was still functional. It would have been
nice to try out a CDRW on it. Anyhow, since CDRWs are still the most
finicky, these well adjusted AGC cicuits could only benefit someone who
buys all Sony CD players, one in their car, home, walkman, etc.

CD