Add a power conditionner or a new breaker panel?

[tima]

Originally Posted by rlw3

... Why does unequal romex length between 2 different 20 amp circuits cause a hum? how perfectly matched do the lengths have to be?

From the experts at Shunyata:

"If you install multiple dedicated lines and the ground wires are different in length - you may introduce ground potential differentials (which cause ground loop problems). Also make sure that the same size and brand of wiring is used for all the circuits. The goal is to achieve equal ground path impedances across all the dedicated lines. If the distance from your A/V system to the electrical panel (in wiring distance) is over 20 feet – I would recommend that you install a sub-panel. Of course, this only applies if you are installing multiple electrical lines for the system. ... Ensure that all electrical lines that service your A/V equipment are exactly equal lengths. Coil excess wiring within the wall if necessary. "