Riaa curve

The RIAA curve for a phono preamp has a 40 dB swing from 20 Hz to 20KHz. Half of that is a 20 dB boost of the bass and the other half is a similar cut in the treble. It crosses the zero point at 1 KHz.

However, it is not a completely straight line from boost to cut.

Obviously the more accurate the curve, the closer your LPs' frequency response will be to flat when you play records.

The frequency response will also be influenced by the interaction of the phono cartridge with the preamp. One can have a preamp with a very flat response that becomes a lot less flat if mismatched to a cartridge.

It bears repeating, though, that this one parameter is not the only one that affects a phono preamp's sound quality. Distortion, noise, headroom and other factors are also very important. The ultimate test is what the user thinks of the sound when he plays a record.

to throw another variable in...

depending on the age of the vinyl, there were several variations of the RIAA curve. A few phono stages even offer switches to adjust to various labels variations on the curve.

Chosenhandle...There is only one RIAA phono equalization curve. Before this was agreed to different labels did indeed use their own propietary curves.

The choice of eq curve is stated on the record jacket, pre 1955. It does not go by year, but by maker. You can search the Internet on appropriate matchings. All the optional eq curves and RIAA are the inverse of that used when cutting the record and should be used accordingly, not for effects as some audiophiles think. I use the EMI and Columbia curve in the Boulder 2008.