Anbody fool around with different pre/amp jumpers?

I am scratching my head about something. I have a modest 45W AMC solid state integrated amp with pre-out and amp-in RCAs on the back. It came from the factory with plated U-bar jumpers connecting the two. The overall sound was OK, but nothing to write on here about. At the time I was using a (very) old Yamaha CDC-715 CD Changer, which was pretty good at the time I bought it, and Audioquest Diamondback interconnects and type 4 speaker cables to my large DIY non-ported bookshelf speakers.

I heard that the sound of these amps could be improved using wire jumpers instead of the stock metal bars and so had some custom silver braided wire jumpers made with gold plated automotive RCA jacks that grip the socket like a vise clamp. I replaced the bars with the wire jumpers and was immediately knocked over by the change in sound - very bright with gobs of detail I had never heard before. The sound was also a bit rough and the bass moved way back but was clear as, well, a drum. The bass came up over time, but I was never really happy with the treble which still seemed overly grainy.

So I looked for another solution. I bought some Audioquest PSC+ copper jumpers for $25. Really well made and nice looking little pieces. I put them in and again, night and day difference in sound. This time the bass came back up, the treble rolled off and the mid range had a nice warmth and roundness to it. I kept these in for a long time and was about as happy as any hobbyist can be, which is not very... (and always looking at better gear)

Over time I replaced the CD changer with a Cambridge Azur 640C v2 with a modest after market power cable, tweeked my speaker positioning, stands and crossovers, and replaced all three fuses in the AMC amp with HiFi Tuning fuses (more on that important change another time). The system was getting more to my liking.

I thought I might try the silver jumpers again, what the heck, it was a "free" tweek. Wow! This time the gobs of detail was accompanied by no graininess whatsoever, just music or silence. The sound was cleaned up to an astonishing degree from top to bottom. Examples, The snare drum on Dave Brubeck's Take Five went from some garbled vibration to clearly articulated metal shimmering against the skin of the drum membrane. Recordings where female vocals have a slight echo, (real or recoding artifact) are rendered so that it feels like my listening room has an echo to it or extends up to 15ft in height. And so on. In comparison, the Audioquest jumpers now sound "dead" on top, like they are masking or garbling the high end signal and the bass sounds boomy. With the silver jumpers in I would still say that the system very much has that solid state sound, but the detail is phenomenal per unit investment and overall the system is punching way above what I bought it for and expected to get out of it compared to what I see and hear in todays market.

So what am I to make of this? I would like to know how a 2" piece of silver wire in a long current path that is mostly flowing through copper can have such a distinct and large effect on what I hear coming out of my speakers and Grado headphones? I could see this happening in a hi end system that is largely wired with silver from stem to stern, and where the copper jumper is the clear limiting factor, but in a low/mid fi system, huh? Anybody else experience this?? Anybody else have an explanation??? Anybody else want to try it????