RIAA Equalization, or Recording Industry Association of America, is a specification for the recording and playback of vinyl records (phonographs). In general terms, the recording is boosted in the high end and reduced in the low end for the recording and the reverse happens during playback. That is, the high-end is reduced and the low-end is boosted. The purpose of this process is to enhance playback, boost playback times, and reduce groove damage that can otherwise occur during playback.
RIAA equalization is not a low-pass filter. It has equalization points in three places; 2100 Hz, 500 Hz and 50 Hz . Implementing this characteristic is not especially difficult, but is more involved than a standard EQ filter. Nearly all hi-fi preamplifiers and receivers had a built-in phono preamplifier with the RIAA characteristic but not necessarily included in modern designs. Add-on phono preamplifiers with the RIAA equalization curve are available; these adapt a to an unbalanced ?10 dB consumer line level RCA input. Some modern turntables feature built-in RIAA standard pre-amplifiers. Special preamplifiers are also available for the various equalization curves used on pre-1954 records.