eSonic2 problem on AJ-500RE in Epiphone Acoustics Posted December 18, 2018 · Report reply Well, which is it, he doesn't know or he does know and it's the preamp? There are lots of sources of "hum" that have nothing to do with the guitar's pickup..... He does know that it's the preamp. The thing is crap and a lot of people have had the same problem with it. What else could the hum be from if not the electronics of the guitar? Obviously it's not the cable or the amplifier.