Here's a question for all you audio files out there. One of my bigger (more expensive) hobbies is sound reproduction. I like "BIG" audio. I like to feel as if I'am actually in concert when I listen to a sound system etc. I also do alot of track ripping for MP3/portabl players etc. I am up to speed as far as the basic understanding of how recording/playing a CD works. The CD is composed of pits and lands that a laser reflects on/off from to produce the digital output which is then converted to analogue etc. What I dont quite understand is this: If a CD is digital (on/off), why do some CDs have lower output than others for the same volume level on the amplifier? I know that many CD track ripping utilities have an option for adjusting volume level to account for this phenomena. But, on any CD the pits & lands are all the same (same depth, width etc) so what causes different volume levels from one CD to another?