Never tried one? They are killer in my studio monitors. I actually bought them initially for my amps, as they make everything more clear, tighter/brighter, but ended up using them for my Studio Monitors.
I actually thought you had meant power
transformer since that's what I know Mercury Magnetics for.
Never tried one of their power cables. Honestly, sounds like snake oil to me. My 4104 is fused for 3A. My power cord (nothing special, came with the amp when I bought it from the previous owner, some BizLink thing) is 18AWG, and measures around 0.12 Ohms from one contact to another (most of which is likely 'cause I'm probing it and not making great contact). If my amp is sucking down 3A, the power cord will drop 0.72V (accounting for twice through the cord for there and back), which assuming the transformer gives a plate voltage of 450VDC for 120Vrms line, is just under a 2V difference in the plate voltage between loaded and unloaded if I did the math right. The cheapest cord Mercury sells is 14AWG, which is about half the resistance of 18AWG, so at 3A load will only reduce plate voltage by a little over a volt. So the difference between my regular power cord and theirs is at max around 1V on the plates, less elsewhere in the amp. And accounting for the fact that 3A is the
fuse current, and the amp is actually rated to operate on about 1.46Arms from the wall (175W per the sticker divided by 120Vrms), the difference between the cords should be about 1/2 V on the plates.
Always possible I missed something or goofed, and resistance isn't
everything to know about a cable, but right now I'm not really seeing how their cable would make a difference. Not saying you're not perceiving the things you say, just that I'm suspicious of how well that perception maps to a difference in the actual sound. Got any clips?