Electrical comes into most homes in the US at 240 volt, phase one and phase two.
This means phase one @ 120 Volts and phase two at 120 Volts. These together such as to a clothes dryer or electric oven is how you arrive at 240 Volts.
If problematic household products are on the phase OTHER than the one your audio gear is on, the stereo is isolated from the pollution introduced by these products. The worst of these are refrigerators, microwave ovens and household computers, although any electric motor or pump is likely to cause noise on the line.
If you look at your electrical panel, there are twin rows of breakers or fuses ( usually running vertically top to bottom ). One vertical row is first phase 120 Volt supply and the other vertical row is the second 120 Volt supply.
Basically if all the stereo gear is connected to breakers or fuses on the same side of the panel, they are more isolated than if they share power with the household products that generate noise.
During new construction or a complete replacement of a panel, have your electrician read each of the two supplies with a VOM. Most of the time they are different.
In my neighborhood, readings are usually around 119.5 for one, and 121.7 for the other. I chose the 121.7 to dedicate to audio.
I have the rare luck to have a three phase drop, and dedicate that to the air conditioning system. This further isolates noise from the audio system and saves power.
This means phase one @ 120 Volts and phase two at 120 Volts. These together such as to a clothes dryer or electric oven is how you arrive at 240 Volts.
If problematic household products are on the phase OTHER than the one your audio gear is on, the stereo is isolated from the pollution introduced by these products. The worst of these are refrigerators, microwave ovens and household computers, although any electric motor or pump is likely to cause noise on the line.
If you look at your electrical panel, there are twin rows of breakers or fuses ( usually running vertically top to bottom ). One vertical row is first phase 120 Volt supply and the other vertical row is the second 120 Volt supply.
Basically if all the stereo gear is connected to breakers or fuses on the same side of the panel, they are more isolated than if they share power with the household products that generate noise.
During new construction or a complete replacement of a panel, have your electrician read each of the two supplies with a VOM. Most of the time they are different.
In my neighborhood, readings are usually around 119.5 for one, and 121.7 for the other. I chose the 121.7 to dedicate to audio.
I have the rare luck to have a three phase drop, and dedicate that to the air conditioning system. This further isolates noise from the audio system and saves power.