The Problem that Dcizmok isn't addressing is that on the AC signal (that is eventually transformed into a DC voltage/current) is system noise. Unless the power supply in your equipment is really well designed and built, the AC noise isn't filtered out/removed adequately and it is passed through the amplification circuitry of your equipment and is also itself amplified. Good clean power from your local utility is the first item to be addressed and believe it or not, if you notice low or high voltage or noise, etc. this is a safety and reliability issue and if you report it in writing, the utilities have a mandate to fix it. I know this for a fact. Second is dedicated lines which means that certain equipment voltage/current isn't shared with the noise making equipment of your house and ground loops are eliminated. Designers get really creative in their circuit designs, but as many really good designers have stated many times, if the power supply isn't designed at the very top of the design/construction level, the system and sound reproduction will really suffer, and many really have no clue regarding proper grounding for circuitry and proper power supply design/contruction. Many times the old saying is still true. you get what you pay for. Lot of people are trying to fix problems that are already inherent in their system, like older equipment that does not use proper internal grounding techniques, or they don't have dedicated lines. So, they will install isolators, conditioners, regenerators, before fixing the real culprit, the quality of the voltage/current coming into your home in the first place. all it takes is written complaints of problems. Too many fixes will eventually choke the system. If the transformer that feeds your house is overloaded, you are starting out with a problem. If you don't have dedicated lines, then you have to turn off all the noise making stuff in your home and wait until the refrigerator stops cycling and the washing machine and dish washer stops. If you have ground loops and hum because everything is plugged into the same outlet, and you are using cheater plugs risking electrocution of yourself, pets, family to fix really simple problem, instead of dedicated lines and elimination of equipment that is quite basically designed poorly. But, I have to say, my system does sound better with my Transparent conditioner than without it. Not night and day different, but you can hear a difference.
enjoy