There's a difference between something "sounding different" and actually being "audibly different."
There are many reasons something may "sound different" while not actually being "audibly different."
Watch the video. It "sounds different" when he's shown mouthing "fah" instead of "bah," but it's not actually "audibly different" because the audio remains identical ("bah" in both cases).
No one has ever demonstrated actual audible differences between copper, silver plated copper, or even pure silver. Nor is there any earthly reason for there to be. And no one has even presented a plausible theory as to why there should be.
So until someone demonstrates that there are audible differences, or comes up with a plausible theory for it, then I can no more believe in audible differences than I can a Flying Spaghetti Monster.
Because you asked me "Do stock cables use copper?" As if it had something to do with anything I'd said. I see now that it had absolutely nothing to do with anything I said or made any sense at all, so I'm going to stop wasting my time with it.
Yeah. RE Designs, before Dan Banquer passed away, used RG-174 for their audio interconnects.
I'd sent a pair of them, as well as some Radio Shack "Gold" series interconnects to Bruno Putzeys, who founded Hypex but at the time was with Philips. Some years ago, John Curl (yes, that John Curl), claimed on another forum that he had measured the effects of "micro diodes" in the wires used for interconnects (a nonsense claim popularized by Audioquest). And he posted some distortion spectra graphs as "proof."
I was suspicious of the graphs as soon as I saw them. Particularly with that big spike up near 16 kHz, which looked for all the world like interference from someone's TV. Plus the fact that John was using some rather antiquated tes gear (in spite of his fame, he couldn't afford anything more modern).
Previously, Bruno had written about some measurements he'd done on some other cables, including some "audiophile" grade cables, and found no distortion that rose above the residual distortion of the Audio Precision System 2 Cascade that he was using.
When I mentioned this to John, he argued that Bruno wasn't measuring the same cables that he was measuring.
So I arranged to send both John and Bruno identical sets cables. Basically they each received half of a stereo pair.
Well, as expected, Bruno's measurements turned up nothing, while John's turned up distortion similar to his previous measurements, which demonstrated that between his antiquated equipment and sloppy setup, that's what was responsible for the distortion he was seeing, and not the cables.
Taking this back to copper clad steel, as I said, I'd sent each of them one of Dan's RG-174 cables. And because of the steel center conductor, would have to be producing some amount of distortion due to the non-linearity of steel's magnetic hysteresis. But not even this was able to rise above the noise or residual distortion of the AP rig. And Bruno was getting down to about -150 dB.