Do not forget that house panels are 208-230 volt in the USA anyway and you should take your outlets from the same side of the panel. Typically break 1 is one side of the panel and breaker 2 is the other side so when you power your room you should use breakers that are all even or all odd. This can also increase the differace in ground protentials. Try stay away from the side your refrigerator or any moter is connected to. Also ask your elecrican if you panel is balanced, meaning even power distribution from side to side, this is not the same as balanced power so do not confuse the two. Some audio equipment is more sensitive than others to this problem.
House Wiring Defect?
Recently I introduced a new power amp connected to my preamp with XLR cables. The pre and power amps were plugged into different outlets in the same room which produced a pretty loud hum from both speakers with the preamp on or off and the power amp on. After the inital freak out and a check of all connections I realized one fix was to power the pre and power amps from the same outlet. This restored quiet operation using either outlet. The question is, does this indicate a house wiring defect or nothing to worry about?