It's an HH Scott 130 preamp. Since I get the hum through both the phono and tuner outputs, I don't think it's coming from the turntable. But when I go to the "extra" output, which currently has nothing going into it, the hum vanishes. There is also no hum when the preamp is off, but the amp is on. I haven't checked all the tubes yet, because it's a major PITA. I just replaced the 6X4 a few months ago.