TDIPablo, "noise" on a power line does not behave the way you think it does. It's quite possible for "noise" to be present at the point of common coupling between the utility and your house and to not be present upstream of that point. As far as cables go, one cable is not the same as another - they have different characteristics and those characteristics are very evident if you study them closely with the right equipment. Having said that, it's not at all obvious to me how those characteristics would result in sonic differences. Properly designed power supplies however, with filtering employed, do result in sonic differences because for one, they lower the noise floor.
