This is what was explained on another post:
It might seem logical to think so but the power cords going from our wall to our equipment is not the last meter of the the power line. It’s closer to the center of the line. Most of the garbage in the line comes from our own equipment. The transformer on the street pole that goes to our dwelling does a more than adequate job of filtering the noise from the grid. It may be that 12 gauge shielded power cords help very little or maybe a lot. There’s only one way to find out.
It might seem logical to think so but the power cords going from our wall to our equipment is not the last meter of the the power line. It’s closer to the center of the line. Most of the garbage in the line comes from our own equipment. The transformer on the street pole that goes to our dwelling does a more than adequate job of filtering the noise from the grid. It may be that 12 gauge shielded power cords help very little or maybe a lot. There’s only one way to find out.