Alan, that’s a kind offer , but “been there, done that.” I’ve tried expensive digital cables [including Ethernet], and once I spent enough time with “wash, rinse, repeat,” and got as much of my expectation bias out of my brain as I could, I had to admit to myself—and my wife—that the cables didn’t make my system better, and that some in fact made it worse. [She heard clocking differences instantly; not digital cables.] When the people who build the equipment—this amazing equipment—tell you that what you need is a compliant Cat 6 unshielded Ethernet cable, we should ask ourselves “okay, why should I believe that an Ethernet cable can make this DAC/Upsampler/Clock sound better?” What is the basis for thinking that the device is made in such a way that one make of digital cable makes it sound better than another? I can see the case for a poorly constructed cable making it sound worse or injecting problems that the DAC works harder to correct, but even a crummy Ethernet cable, or a shielded one, is likely to deliver a bit perfect stream. So, what’s happening to make your brain and ears hear something different? I don’t know. I believe you hear it; I also believe that psychoacoustics are the more likely explanation. As you said:
I know the audiophile mantra all too well: “I don’t understand why or how, I only know what I hear.” And it is completely valid, because each of us is the only person who has our ears and brain. No one else can hear what we hear. I also believe that everything matters. It does. The physical world quite literally cannot exist unless everything matters. But that doesn’t mean everything produces a discernible difference. The simple test of unplugging one’s Ethernet->DAC cable demonstrates that certain physical changes can stop making a difference. Two different 110 Ohm AES or 75 Ohm BNC cables can produce visually different, but sonically identical, eye test patterns. Every thing matters, but some differences don’t.
Good luck with that Vivaldi stack. I have reason to believe you will love it!