I agree with Ted W. - no matter what the power co does, you will continue to have this problem. Here is why:
When two pieces of equipment are connected via an unbalanced interface, the noise current flows in the shield conductor of the cable. Because the shield has impedance, a small noise voltage drop appears across the length of the cable, according to Ohm's law. Since the cable shield is also part of the signal circuit, the noise voltage will be directly added to the signal at the receive end of the cable, which is the sum of all the voltages in the loop from point A to point C. Because the shield impedance is part of two circuits, noise current and signal current, this mechanism is called common-impedance coupling.
Consider this typical scenario. Two devices are connected by an RCA audio cable. Both devices have 2-prong power cords, and their power-line capacitances cause a 300uA, 60Hz noise curent to flow between them through a typical 25-foot unbalanced cable. The cable has a foil shield and a 26-gauge drain wire, making its resistance, or 60Hz impedance, about 1 ohm. Using Ohm's law, we calculate the resulting voltage drop to be 300 uV. With respect to the nominal consumer signal reference level of 300 mV, this noise level is only 60 dB. And the high-frequency noise may be even worse and more audible as buzz.
The magnitude of the noise current can be much higher if both devices are safety grounded (i.e., having 3-prong power cords). Referring to Figure 1, consider that leakage currents from all devices on a branch circuit cumulatively flow in the safety ground wiring. Since leakage currents for safety-grounded devices are not limited to the 0.5 mA allowed for 2-prong equipment, it is not uncommon to have leakage currents of 100 mA flowing in portions of the safety-ground wiring. Because of the impedance of the safety-ground wiring, this could result in well over 10 mV of noise voltage between the safety ground pins of two different receptacles.
And this can get much higher between two outlets on different branch circuits. For two safety grounded devices, this voltage will be impressed across the length of the signal cable shield and be directly added to the signal. For 10 mV of noise voltage, the noise would be only 30 dB with respect to reference level.
In a standard video interface, reference level is 1 volt peak-to-peak, including sync. The active range from reference black to reference white spans about 600 mV peak-to-peak. Since our previous noise voltage of 10 mV (rms) equals about 30 mV peak-to-peak, our signal-to-60Hz hum ratio would be 26 dB. This would cause a visible hum bar in a video display. Even higher voltage differences can result if one of the devices is connected to an outside ground point such as a separate earth ground or a CATV drop.
The above has been copied from:
[Link: svconline.com](but I did stay at a Holiday Inn Express last night!)
I had this same problem a few years ago where an 80" Mits RPTV, which was located on the other side of the room from all the other equipment, kicked my a?? with video noise and I never really understood what the heck was going on.
Here is the room -
[Link: genelarge.com] click on Media Center
-yes that is a Bose Lifestyle 30 system which I did not sell them! It was all changed out at a later date-but the video noise stayed. The equipment (DSS, DVD, VCR, A/V Receiver, etc) was in a cabinet in the back left corner of the room.
Sorry for such a long post. This house no longer belongs to the owner of the website above so please do not call.