well, i think one is gonna be the ac to dc inverter although there are chokes available to filter this out probably a quality test bench power supply would have good clean power out this alone would probably be above the cost of a good home amp,and then another could be a "floating ground" i came across this on an amp in my truck,turned out to be a really stupid problem(little tear in the shield of my sub amp cable) but the term just makes me think that electronics like a good ground and i would think that intermixing different (car and home) would not be a good idea if any level of quality is to be maintained.although i do remember using the speaker level out on my sound-design receiver to feed a pyramid eq/booster(battery charger powered) to power 12" stromberg carlsen speakers 20 years ago.