An equalizer is a "brute force" solution. Preamps once had "scratch filters" that basically rolled of response around 6000 Hz. This will help with the continuous surface noise, but won't help pops and clicks. Various electronic devices were developed specifically to address continuous surface noise and the occasional pop and click. Some worked quite well, but all were made obsolete by CDs.
Very effective noise reduction can be done if you don't try to do it in real time while the LP is playing. Basically you digitize the signal and analyse it with a computer program to distinguish noise from transients that are part of the music. For example: Music transients have a sharp leading edge and a gradual decay, whereas a groove defect has sharp leading and trailing edges. (So if you play the recording backwards, any transients are noise). I have heard recordings that are almost a hundred years old both before and after processing. After processing the sound is sometimes as good as an LP from the 1950's. Interestingly, once the noise is striped out HF boost can be applied which reveals unexpectedly extended HF signal that noone knew was there because it was masked by the noise.
Very effective noise reduction can be done if you don't try to do it in real time while the LP is playing. Basically you digitize the signal and analyse it with a computer program to distinguish noise from transients that are part of the music. For example: Music transients have a sharp leading edge and a gradual decay, whereas a groove defect has sharp leading and trailing edges. (So if you play the recording backwards, any transients are noise). I have heard recordings that are almost a hundred years old both before and after processing. After processing the sound is sometimes as good as an LP from the 1950's. Interestingly, once the noise is striped out HF boost can be applied which reveals unexpectedly extended HF signal that noone knew was there because it was masked by the noise.