Jdec, on the contrary, pardon my less than qualified attempt at explaining star grounding.
Essentially, everything gets plugged into a single power source, such as a power strip, sharing a single ground.
As switching amplifier technology progresses we are seeing less and less of the RF and EMI issues that some early designs produced which seemed to pollute the AC line.
If you are using different legs (breakers) of an AC system to power a system simply try using only one leg.