RIAA equalization

RIAA equalization is a standardized curve, set by the Recording Industry Association of America, that is applied when a record is cut and then reversed during playback by the phono preamp. Bass frequencies are reduced and treble frequencies are boosted when a record is cut, and a phono stage does the opposite on playback.

This curve exists because a record groove cut with full, unequalized bass would need to be far wider to avoid the stylus jumping out of the groove, while unequalized treble would be buried in surface noise. Applying the RIAA curve in both directions lets records pack far more music into a smaller groove while keeping noise low, and it became the standard essentially all vinyl records made for decades have followed.

In practice, this curve is applied automatically by any proper phono preamp, so most listeners never need to think about it directly as long as their signal passes through one before reaching a regular line-level input. The main relevance for buyers is confirming a phono stage genuinely includes RIAA equalization rather than just amplification, since a preamp that boosts volume without the correct curve still leaves music sounding thin and harsh. A common misunderstanding is assuming any generic preamp will work for phono, when the RIAA curve specifically separates a proper phono stage from ordinary line-level amplification.