I was a bit anxious, but mainly very curious, when I bought a 4c single crystal copper (no silver plating) Xinhs for my Meze Advar. The Advar is by nature quite bright with a serious peak on 8KHz. As I can't always EQ it everywhere, I wanted to try out pure copper instead of the silver plated default cable that comes with it. The only other difference in my setup is that my copper cable is 4,4mm whereas the silver plated is 3,5mm. Both go into an iFi Go Bar.
Well, the cable does what I want it to do. It rounds off the highs much better. With silver plating, they're not so much harsh, just too prominent. With the copper, it's much more acceptable.
I like it to such an extent that I'm considering getting a silver plated version of the same cable for my Audeze LCD-2 closed back. I contacted Xinhs via AliExpress chat to ask if he can do the mini-XLR connectors for that headphone and he replied immediately, yes, with $10 surplus. I'm currently using this headphone straight on the headphone out of a rather esoteric audio interface Expert Sleepers ES-9. It's an audio interface that sits in a modular synth. The idea is to take the balanced jacks out, send them to an L30 ii, and plug the Audeze with the Xinhs into that. Very curious, and a bit anxious, how that will sound!