Everything goes through break-in. Even a cable used every day, if you unplug it and move it around, will not sound very good at first.
So what you did, in addition to adding a new part that will take some time to burn in, you also moved the cables around a lot and subjected the wire ends to bending being screwed in. The sound you describe, "hollow and confused" is exactly right. Heard it many times myself.
None of this is anything to do with the part itself, which may turn out to be part of the problem. In other words it may well turn out to be that it never sounds good no matter how many hours it gets. I’m simply saying what happens, because obviously hardly anyone else has enough experience (let alone the listening chops) to know. (Like hex screws, that’s relevant, wow.) (Notable exception, salectric.)
And now for the grande finale, the piece de resistance, the proof in the pan, take one cable- any cable- from your system. Power cord, IC, I don’t care. Listen to some good music. Unplug it, bend it, wriggle it, plug it back in. When you hear the same confused sound and notice it only lasts a few minutes, then you will know I know what I’m talking about.
By the way its great that you noticed this and thought to ask. Its just your bad luck the first few to reply don’t know this stuff. They should. I’ve been posting it for years. They’ve had all kinds of chances to learn. Oh well. Good Lord, one with nearly 10k posts thinks you hooked it back up out of phase. See how clueless? Be careful whose advice you take. DYODD. Go and listen. You will see.