Wrapping power cords and interconnects with copper foil.

……why not listening to your with and without the copper foil as well as with and without taking a gummie and let us know the difference. Now you know why some laugh at this hobby . Why would even think of doing this and better yet who cares ? 

Here. Just build your own correctly out of the shielded power cables.  I'm a big fan of the DH Labs 14 gauge, shielded: https://partsconnexion.com/ac-power-bulk-wire-cable/

If i was sensitive to laughing and mockery i would never had created my own system/room by experiments  which put me now  in ecstasy at peanuts costs...

I would had given 50,000 dollars( i dont have) for that and called it audio done...

And human nature being human nature i could be here mocking my own ghost because he insist too much on the fundamental and only way to improve any system at any price : mechanical,electrical and especially acoustical devices controls of the room/system...Not upgrade first and last but optimal means of controls.

Not sleepwalking consumers buying power but basic knowledge in acoustics and other basic tools.

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. 

@joelepo Yes, good practice is to keep power cables away from audio and data cables, as far as practical.  If they have to coexist, try to cross them at right angles or thereabouts.