I agree that having both hooked up to the same circuit but different outlets SHOULD not be an issue but a loose screw on the ground terminal anywhere in that circuit could cause the problem. Tripp-lite makes good equipment and should easily handle your equipment. I would take another look at the circuit your TV is plugged into and make sure all the connections are tight since the hum is slightly present. Is the Tripplite big enough to handle all of your equipment?
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner