Thanks everyone for your help, especially Jsawhitlock. I checked out the psaudio site and they have a great hum wizard. As it turned out my phono pre was sitting too close to the amp. I rearranged the configuration as well as put an aluminum shielding jacket on my cables and the hum nearly went away. It's now barely audible when I have it turned up to 3 o'clock, which is passible for now. I'm going to experiment with some better shielded cables since I can't get the components any farther apart in my rack. Hopefully that'll carry me the rest of the way home.
Thanks again!
Thanks again!