Since record­ings are cap­tured on vinyl within the grooves and lower fre­quen­cies re­quire greater side-to­side move­ment of the sty­lus, and cor­re­spond­ingly wider grooves, re­duc­ing the groove width will al­low for more grooves and cor­re­spond­ingly longer record­ings to be cut to a vinyl record. A method to re­duce the groove width is to equal­ize or al­ter the fre­quency re­sponse (re­duc­ing lower fre­quen­cies) of the record­ing be­fore it is cut. In the 1950’s a spe­cific equal­iza­tion stan­dard was agreed to by the Record­ing In­dus­try As­so­ci­a­tion of Amer­ica (RIAA). RIAA equal­iza­tion al­lowed for nar­rower grooves through at­ten­u­a­tion or re­duc­tion in low fre­quen­cies. The ma­jor­ity of records use RIAA equal­iza­tion and there­fore, are not cut with the orig­i­nal true (flat) fre­quency re­sponse of the orig­i­nal record­ing but rather, a sig­nif­i­cantly equal­ized ver­sion. In or­der for the orig­i­nal record­ing fre­quency re­sponse to be re­stored, it is nec­es­sary to re­verse the RIAA equal­iza­tion and this is where the phono stage is cru­cial. The phono stage ap­plies an in­verse (or op­po­site) RIAA equal­iza­tion curve to the di­rect sig­nal out­put re­ceived from the turntable. Es­sen­tially the phono stage boosts the low fre­quen­cies and re­duces the high fre­quen­cies in a man­ner that nul­li­fies the orig­i­nal

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