Text: Equalization, in a general sense, refers to any deliberately introduced change in frequency response. It is used, for example, during disc recording to boost the treble range and weaken the bass range. During playback, an opposite equalization is applied to restore the original tonal balance. The treble range is emphasized during recording so that when the treble is reduced in playback, the record's surface noise will also be reduced. The bass range is reduced during recording in order to prevent the cutting stylus from overcutting the groove at low frequencies. As the term "equalization" implies, everything comes out "equal" in the end, hopefully with flat overall response between microphone and loudspeaker. Since 1955 all records have been cut for playback with the RIAA (Recording Industry Association of America) equalization curve. Either the playback amplifiers provide equalization in their preamplifier stages, or the cartridge itself compensates for the RIAA curve. Tape is equalized both in recording and in playback to compensate for the inherent high and low frequency losses in the recording process. In addition, there are different equalizations for each tape speed on most tape recorders, the correct equalization for each speed is automatically switched in when the speed is set.

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