Yes, cables do make a difference -- regardless of price...

@decooney Sure, but also note that the NASA email (granting it's authentic) is concerning a laser diode application that bears little resemblance to audio-scale electrical properties.

So, the test is very simple: take a high resolution audio stream consisting of music (you can do single tones/sweeps later). Connect the streamer to an excellent DAC using modern USB cable. Connect DAC analog output to excellent ADC using Test Cable A. Record audio. Replace Cable A with Cable B (try a bunch of budget through to expensive). Record, record, record. Align the digital signals and subtract them from one another using standard software tools. Any residual signal represents differences between the cables. If the residual spectrum is bass-rich, that might be called "tubby" by the subjectivists. More high frequency might be called "more resolving." Fair enough! 

OK, so we looked at analog XLR interconnects in the above scenario. We can also do speaker cables by getting a calibrated microphone like the Umik-1 from MiniDSP and recording the track again through the streamer > DAC > amp > speaker chain. Swap cables and then compare once again to look for why folks think there's an obvious difference.

Do the same kind of thing for power cables, power conditioners, ethernet cables, etc. There may be differences! The SPDIF cables from 2013/2017 mentioned in posts above showed flaws, but SPDIF is notorious for jitter issues, especially in the old days.

We need some exciting results for the other categories of cables!

@chocaholic 

Re: mains connection 

Poorly designed components (or components that didn’t look at this issue) can have leads that act as TRANSMITTING  antennas of noise.

Given the rats nests of interconnects and power leads in the back, I wouldn’t be surprised, at all, if an interconnection doesn’t pick up garbage transmitted back out from an unshielded power cable, especially if they are touching and follow parallel for a fair length.

My theory is based on a sample of one, where the power cord of my turntable laid flat against my phono cable and I could (and anyone could) hear a hiss until the two were pulled apart.  Kept happening due to how everything was smashed together in my original set up.

Went away when I switched to an Amazon (nothing fancy, but definitely shielded, you can’t detect current with a “live wire” detector) mains cable.

Mind you, the phono cable is the thinnest interconnect and the MC signal the weakest signal in the chain.  So the most vulnerable.

When I redesigned my rig, it made me run all interconnects XLR (including phono), picked fully balanced components (including phono amp) and took great care lay out wiring with a considerable air gap and no touching.

it’s also super sharp looking behind the scenes which makes my OCD very pleased. LOL.

Not fancy wiring, either.  Mogami platinum with high end furutech ends.  Speaker wire is larger gauge pure silver from a military aircraft (used for fire reasons), braided by my daughter.  I doubt all in its $1000.

@davetheoilguy A shielded cable of proper gauge can be had for $20. I think we’re making the same point. I believe most proponents of costly power cables do so not primarily because of shielding, as that’s a given. Rather they are able to hear a sound quality difference.

I personally can hear no difference between shielded power cables. That leaves me with the opinion that a costly power cable that carries no audio signal will not be my choice. Others with a different opinion or experience are certainly welcomed to do as they please.  But shielding alone is not a reason to spend thousands on a short run of electrical cord. 

@chocaholic 

I think we are talking the same point, or close.  I'm certainly not going to spend thousands on a main.  But $40 (probably was $20, but Washington DC has been printing money for some time now) on a shielded power code is good insurance when dealing with cramped wiring at the component end.

My long runs (to right sub and two to phono preamp), btw, are nice, medical grade, cables stolen from a broken MRI machine.  Other than really nice plugs, heavy gauge, and length they are not particularly exotic.  I suppose they have no ferrous alloy of any kind, but I'm not sure that's relevant. I just ran them along the wall in typical Home Depot wire routing "tubes" to keep them neat and untangled.

Herman sums it up perfectly.

The only exception for mine is the shielding capabilities.

Some manufacturers claim to be kings of shielding and charge you an arm & a leg for the privelage. Yet can be out-performed by a cable 30% - 50% cheaper that also generally (but maybe not always) produces something of a much higher standard & finish (in terms of materials, craftmanship and technically superior).

Mogami is a great example of the later. The Chord Company a good example of the former.