Without talking about cables made with unobtainium, where did you start hear a difference.
@curiousjim The first time I heard a power cable make a difference was at CES in 1990. I was visiting George Cardas where he was showing of a set of Magnaplanar MG3s that had a custom wood frame that was built to be both stiffer than the original frames and non-resonant. He took an interest in the amps we were showing and I was interested to see how the speakers worked with our amps, so I brought our MA-1s over after hours. We played the system for a while. It sounded good, better than I remember MG3s ever sounding.
George then suggested we try a set of his power cords on the amps. We did, and immediately the system got better across the board. The bass, which by comparison seemed a bit ponderous, became nimble and fast with better impact. I was not sure that was the difference so I arranged the cables behind the amps so I could switch them in a couple of seconds without having to shut the amps off. The difference was immediately audible in either direction- better with the Cardas cables and worse with the stock cords. I bought them on the spot and still have them.
Years later I sorted out why they worked so well. The MA-1s draw a lot of power and the voltage drop across the stock cord was enough to reduce the filament voltage and B+ at the same time- so the amp made less power. The Cardas cables simply had less voltage drop.
The take away is if you have a lot of current draw you’re more likely to notice a difference with power cords. If the equipment has well regulated power supplies with good headroom you’re less likely to hear a difference. That explains why power cords don’t seem to affect our MP-1 preamp or class D amps all that much, but affect our OTLs quite a lot.
So you might look to see if power draw has anything to do with it in your setup.