Wrapping power cords and interconnects with copper foil.

@donavabdear Neville Shute (Norway) said that an engineer was somebody who could do for 10 bob what others could do for a quid.  In other words, provide very cost-effective solutions. 

Understanding some basic physics would save some hobbyists thousands, if not tens of thousands, in my opinion. 

I am not sure if you meant "Sad people" or "Sad, people ..." or even what you meant by "the foundation of their hobby".  Taking out the double negatives from "Unfortunately this is not a group about engineering" gives "Fortunately this is a group about engineering" but I suspect you meant the opposite!

Acoustics include psycho-acoustics and is not what is usually discussed in audio thread : room panels...And audio journey include also musical knowledge ...

Myself i lamented about how people experiment so little with the ground root of their hobby , not engineering, sorry but acoustics. not branded name of tubes or digital gear but the link between gear-speakers/room/brain-ears...

Most Engineers in all fields as the average men buy a piece of gear and called this audio if they had bought the best reviewed product; they are only divided between the value of measures versus  how they feel after listening ... This is what people called audio journey .... Not me and some others more enlightened one ...

Acoustics experiments is the core not only of audio experience but of the musical and sound understanding.

Unfortunately this is not a group about engineering or physics most people here seem to be interested in the hobby more than the engineering principles. Sad people who love listening to music so much have such low regard for the foundation of their hobby.

Where would you even get copper foil? Aluminum foil is common but not copper.

Aliexpress

@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😂