PC Speakers

[Fidelity 26]

quick question.. does this hum change with signal wires unplugged? how about with them plugged in.. Sometimes these amplifiers are grounded (why?.. computers are always grounded.. laptops generally float) and earth loops are common.

Not sure as atm there no hum and Theres 4 cables i wired in =mains .1 mini din type plug.1to the ither spaeker and the other to the pc. Not wirefree.