The problem of induced hum comes from running power lines in parallel, in close proximity, for long distances with your signal lines.

Crossing at 90° presents no problem. Speaker level signals 6" away from the power should also be just fine.

Really to induce noticeable hum, you need to wire-tie a 15' extension cord running a space heater to your line-level coax. Then you'll get something. Otherwise, with even a modicum of care you'll be fine.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris