Please do tell more about that metallic noise.
Uhm… You could describe it as a slightly buzzy, decaying echo underlying the otherwise clean presentation. Clearly audible with quiet pieces like piano solos, less so with stuff that's fuller and noisier to begin with.
Don't know how to describe it. Words are hard.
Edit:
Speaking of a piano… Imagine putting down a very fine, light, metallic wire across the strings of a piano, and then play something. That's pretty close to what it sounded like.
Was it a mechanical rattle?
Mechanical rattle? In the left channel of an amplifier? How do you figure that would work?
Well, if it ain't mechanical…
Beats me. I still don't quite know my ass from my elbow when it comes to analog amplification circuits. Well, I do know a little bit. But that's mostly just theory and definitely still not nearly enough to diagnose an issue just by listening to the thing. You have to first break and then fix a
looooooooot of stuff before you can do that, so maybe ask me again in a few years.
Also, I'm definitely not opening the amp to poke around in it with my scope. At least not for as long as it's under warranty.
But I had a similar sounding issue in the past with a different audio product and it turned out to be a faulty capacitor. So maybe it's a faulty cap somewhere? ¯\_(ツ)_/¯
Won't know for sure, though, as the good folks in Valencia only really tell you what the problem was if and when they return a repaired unit to you — which will not be the case with this one because it'll be replaced, not repaired.