hum with phono on adcom preamp need help

Make sure all your components are plugged into the same
grounded circuit/power strip. Buy an isolation transformer-connect it to the same circuit, you can power up only one of your components from the isolation device, otherwise you may loop the hum thru the transformer. Try each component until you either eliminate the hum or strike out. If you have balanced outputs/inputs from your pre to your amp use them. If you have a cable connection to the system purchase an inexpensive isolation transformer for your cable box {www.partsexpress.com}-- good luck-

I had the SAME problem, I had 3 turntables hook up to
a pre-amp (NOT at the same time of coarse), and I kept getting the feedback noise that you have now.
There are 2 RULES, that I learned when I solved this problem.
1. DON`T have your TT. close to your speakers!
It should also be isolated in a rack, on it`s own
shelf, AWAY from any speakers.
2. Your TT. cables that go in to your pre-amp
CAN`T be touching each other! And NO other cables from
ANY other unit in your system can touch them either!
Just by doing these 2 things I got rid of the
feedback. Make sure nothing is touching those
Turntable cords back there, and you should be fine!