> you need to reverse the RIAA curve to get
Audacity has a built in 'equalization' effect with presets for several
disc cutting curves, including RIAA. I'm not sure how you would use
it to reverse the curve though - it looks like it was designed to add
vinyl/shellac equalisation to digital recordings, rather than remove
it from analogue ones recorded without a correcting pre-amp.
The alternative for early recordings is to use an old-school pre-amp
with analogue settings for the different curves used before RIAA
became standard, such as a Leak Varislope:
You need two for stereo, and because most Leak stuff is 'collectable'
they are often sold for high prices. They weren't exactly cheap back
in the 1950's though.
I sold my mono Varislope, and these days I use a Musical Fidelity
X-LPS for everything, because I now have a modern pickup cartridge
designed for 78s (an Ortofon) as well as another for 33/45s. The
sound of the 78s probably isn't
These units are discontinued now, and you can pick them up quite
cheaply from 'end of line' hi-fi dealers - mine cost £100. They go
for more on eBay than the brand new price, so watch out for that!