I stopped by vintage audio collector's house the other day and there was this old valve pre-amp that intrigued me. It had a control knob on it for various record labels, eg Decca, Columbia, RCA etc. The guy at the place explained that it applies the correct RIAA curve for each of the labels as standardisation did not commence until the late 50s and was still being rolled out into the 60s. Having a few old 50s and early 60s records that got me thinking. Does this mean to get the optimum sound from these records I should somehow implement a variable RIAA curve specific to each label? Has this already been done or am I missing something?