Grounding A Preamp

All the inputs except phono are dead quiet. I do know how to wield a soldering iron, so I guess I'll have to get out the Fluke meter, and tear apart the preamp...

The TT does have 2 prong plug. To check if the TT was the offender, I completely disconnected, ground wire and all. the buzz was still there. To this untrained ear, it sounds like a 60Hz buzz, like you'd get from a fluorescent light, or a wall-wart transformer.

The preamp also has a 2 pronged plug. The buzz is coming from the speakers, and is volume dependent.

I didn't check the interconnects for corrosion. I did change the ICs that go between the amp and the preamp. allow me to clarify one thing: when I touch the preamp, SOMETIMES the buzz goes away, but not always. I figured that if I stopped the preamp from buzzing, I would leave that unit powered on while not listening. The amp, and everything else was shut off. That practice didn't work either. The buzz was there when I turned the amp on again.