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What is the Agc. range? I was reading a thread on audiokarma about why older CDp's and even some newer ones will not play burned CD's and someone said that the AGC range is often not enough for the player to read the CD.
When a CD player reads a disc, it fires a laser into it and looks for reflected light modulated by the pits in the reflective layer. Normal manufactured CDs have fairly well controlled reflectance, but there is still a variation in the amount of light reflected back, which affects the ability of the player to read the pit pattern without errors. So, when a disc isn't as reflective, the player cranks up the laser power and/or the gain of the reader to compensate. If it's highly reflective, they back things down. The action is generally called AGC for Automatic Gain Control, though I think that's not exactly the right term for this application. In repair manuals its not aways called AGC, but the function is the same.
A recordable disc may have a much wider range of reflectance, usually lower than a normal CD, and that's part of why some players have trouble with recorded discs. A players AGC range is the range of automatic adjustment that can compensate for disc reflectance variation. If a disc is just not reflecting enough light, and the AGC is all the way up, the read errors will be huge and the player may either not read it at all, or be very erratic.
CD burners usually have highly capable readers, so it's practical to copy the problematic disc to a better blank and solve the issue.
Players also age, and laser power does decrease over time. Older players may not have the ability to read a CDR anymore because of lasers aging out. There used to be adjustments to compensate for this, it should all be automatic now, right up until laser failure.