Wrapping power cords and interconnects with copper foil.

Thanks!!! for possible great idea to resolve a similar issue. I was considering aluminum foil.
When we added two Dolby Atmos "height" speakers to our theater system we got not so loud, but annoying, 60Hz hum from the height speakers.

At first I blamed the AudioSource AMP210VS 2-channel amp bought from Crutchfield to power them. Who wants to pay for greater than 100dB below your program to hear a hum that is 60dB? The amp requires single-end RCA connections to pre-processor, so I tried a few decent cables.

Finally... my wife simply moved -- an inch or two--the multiple 120VAC power cables routed from surge protectors and APS from the audio cables: Hum GONE... inaudible! We could tweak attenuation of the hum in real time. 

Later experiments revealed just a couple centimeters or orientation of the 120VAC power cables relative to the RCA or XLR cables made a world of difference! 

Hope this helps... We really appreciate Audiogon posts that enhance our system. 

@richardbrand Agree that right angled cables minimize transfer of electromagnetic signal... Parallel cables promote transfer, much as transformer or RF coils are wound in parallel with each other. 

But... for the whole group.... do want to remark the following: Copper or aluminum shielding is NOT a “snake oil” fix— as some have posted— but rather is based on established principles of physics. Shielding of audio cables from electromagnetic applies function of a "Faraday Cage," which creates a barrier between the internal components of a device and the external electric fields.

@richardbrand  I think many folks posting here enjoy diving into the physics and engineering of the media and equipment that deliver sound in high fidelity. Their curiosity may be driven by the product  of such engineering as much as their love of music and theater. As a university research scientist, e.g., a natural nerd, I may be wrong😂