#1
i have a g&l legacy through a peavey classic w/cannabis rex speaker, and i've noticed that the tone is sort of closed, like someone singing "mmmmmmm" instead of "ahhhhh".

i notice it when i start playing, so i don't know if it's cold tubes or something. after i've been playing for a while, i'm too used to the sound to be aware of it one way or the other.
#2
get a BBE sonic maximizer?
Self proclaimed prophets are great people...
#3
how old is it? maybe you need to change the tubes...

it could also be an EQ issue... play with the knobs a bit and see if you can brighten it up... or purchase an EQ pedal
#4
Yeah, sounds like maybe you are not running enough treble? Or maybe even just too much mid. Just mess with the EQ's and it can make a huge difference.