Why does my vinyl sound so bright?

If the only thing that changed is the wall mounted shelf, then there is a very good chance that is where the issue.

I've never wall mounted a TT, but I would think it would be harder to get the leveling, isolation, and perhaps other factors right, in general. Not to say it can't be done.

IS everything level? Any damage or changes to cartridge alignment in the process?

Arthursmuck, there's great advice here. Turntable levelling, VTA, tracking force can all contribute to bright sound.

If the VTA is "tipped up" at the back (a high arm post) the highs may be emphasized at the expense of the bass. If the turntable is out of level, the force exerted on the stylus may change angle and give an effect similar to high VTA. Also a reduction in tracking force (if the arm counterweight shifts) will press the stylus down less into the groove and that can change the tracking angle.

If your sound is brighter but also clearer, less muddy and rumbly, that's a sign you have eliminated feedback at the low end by installing your TT on the wall shelf. If this is what's happened, the feedback in the old setup may have been masking a brightness problem.

The wall shelf is mounted directly into the studs, however it is an inside wall as an exterior wall was not an option. Regardless, the wall shelf has made a significant difference as the system is on the second floor, previously when walking across the room the TT would bounce, now it is very solid and stable.

I'll look into the mutliple things given here and report back after some experimenting. Thanks everyone, for helping this vinyl imbecile without making me feel like more of one.

Arthur, it's gotta be the move to a wall mount, it doesn't take much to change the character of a TT when changing platforms. I also have the blackbird and it is very revealing.

Okay, this is weird. I adjusted VTA a tad and validated VTF at 2.0 and now music sounds garbled and warbly coming out. I'm guessing the cartridge may have bit the dust or be biting the dust. Maybe the cantilever got damaged somehow when I moved it (although I had the arm secured and it was a pretty short and uneventful trip from rack to wall.)

Any further thoughts?