Sometimes power conditioners will stop noise problems by placing equipment on different, electrically isolated outlets. This is done using isolation transformers. Sometimes this is ineffective however, due to the differences in internal construction of different power conditioning equipment. Some safety regulations, such as UL 1950, specify that an isolation transformer is only allowed to isolate the hot and neutral wires; the grounding wire must be passed straight through. If this is the case, the ground loop problem may still exist because many communication circuits are connected to the grounding conductor and not the neutral. In this case, the isolation transformer, or any power conditioner or UPS with an isolation transformer will have absolutely no affect on the grounding problem.

The noise may be generated externally, from a dimmer or refrigerator compressor for example, and coming in through the main power input on the audio video equipment. In this case, a high quality power conditioner may be effective in reducing or eliminating the noise problem. You may also find that one of the signal interconnecting cables in your system is faulty. This can also cause noise problems. Check for this by swapping the cables with one that you know to be good.

You can solve most noise problems in your home theater or multi room audio/video system by taking the systematic, step-by-step approach. Work your way up the signal chain, eliminating each piece of equipment as you go. If you have nothing connected to your speakers except the speaker wiring, and they still hum, the problem is noise induced into the speaker wiring from adjacent power cables. Other than that case, most problems are caused by ground problems, which you can find, and solve, if you take it one step at a time.