Is your power underground or overhead. Have been a lineman for Florida Power & Light for 12yrs. and now a lineman for a municipal power company. 4kv, 12kv, 23kv, and so on can be single phase, two phase, three phase. Most of the time when power is brought into a neighborhood it is a three phase system, but one phase will be sent to one part of a neighborhood, another phase to another part, and then the other... Normaly it is a single phase primary that energizes the coils in your particular transformer, then it converts your primary voltage (4kv, 12kv, 23kv) down to your 120v-240v for use in your home. Overhead primary systems can create a problem called TVI. Which is television interference. This used to be very common back when rabbit ears and antennaes were used for TV reception, it also caused hav'oc with HAM radio operators. The cause was the hardware on the poles were not properly tightened or became loose. Normally, going to the pole that your property was associated with, and one pole up the line from yours and one pole down the line from yours, and re-tightening the hardware fixed this problem. If you have underground power, then there is no problem with this type of interference. 3 phase, 2 phase, or single phase. All of the primary conductors are insulated. Now whether or not the overhead type system can cause interference whith a stereo system, other than FM reception, I would doubt it. I won't guarantee that, just because my knowledge is rather in a limited area. An electrical engineer could probably answer you more completely, as they are proficient in electrical theory. I am not saying you don't have a problem with your electrical system bacause I am a lineman, I am a stereo enthusiast myself. The problem very well could be in the electrical system of your home or equipment. Don't know if this puts your mind at ease with your power provider, but I hope it answers some of your qustions about 3 phase power. Sincerely, Skip.