RIAA equal­i­sa­tion

Computer Music - - Make Music Now / Virtual Vinyl -

Es­tab­lished by the Record­ing In­dus­try As­so­ci­a­tion of Amer­ica in the 50s, RIAA equal­i­sa­tion of­fers longer record­ing times, im­proved sound qual­ity and re­duced play­back wear.

An RIAA EQ curve pre­em­pha­sises the high fre­quen­cies in pro­gram ma­te­rial by ap­ply­ing a +20dB high-fre­quency boost with a cor­re­spond­ing -20dB cut to bass fre­quen­cies. By ap­ply­ing the RIAA EQ curve di­rectly be­fore cut­ting the mas­ter lac­quer, the bass is re­duced sig­nif­i­cantly, mean­ing grooves can be spaced more closely for longer record­ing times. To achieve a flat fre­quency re­sponse on play­back, an op­pos­ing de-em­pha­sis curve is ap­plied to the pro­gram ma­te­rial by the play­back equip­ment. This not only bal­ances out EQ ap­plied be­fore cut­ting, but also ma­jorly at­ten­u­ates any high-fre­quency arte­facts present.

Though this process shouldn’t the­o­ret­i­cally have an over­all ef­fect, there’ll usu­ally be some phase dis­tor­tion in­tro­duced by the EQ fil­ters used for pre­em­pha­sis and de-em­pha­sis, as well as rum­ble as the turntable’s mo­tor is am­pli­fied by the large de-em­pha­sis bass boost.

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