Well my Wadia DAC has these lights that show the bitrate of the discs. And it also has a light called "Emphasis". So far i only seen it on the "Hair Live" disc. Do you own such discs too?

Acording to the manual it is:

Some discs have been encoded with a equalization process called emphasis. While giving "better" measurments, these discs always sound worse than they would had this process not been utilized. All compact disc players recognize discs that have been encoded in this way and then "de-emphasize" the digital signal prior to the digital to analog conversion. The Wadia 12 digital to analog converter notifies the user that a disc has been encoded in this way through the illumination of "Emphasis".