Ground loops are created whenever an audio ground is established at more than one location. Theoretically, the only place the audio ground should be connected to the chassis ground is at the source unit. In my experience, I've found that in systems that have noise problems, a ground loop is the culprit nine times out of ten. Never run signal wires alongside power cables . This is especially true in installations where high powered amplifiers are used.
Large amplifiers are capable of drawing large currents.
These currents vary with the musical demand of the program material as does the electromagnetic field surrounding the power cable. The more current that flows through the wire, the bigger this field becomes. If audio cables are located in close proximity to this fluctuating electromagnetic field, noise could be induced into the system. This will insure maximum protection against induced noises by power cables and other sources of electromagnetic interference. Good audio cables are not cheap.