#1
I own a crate v33 212 came with stock el84 power amps tube and i believe stock stock Sovtek preamp tubes im not sure on the exact name and type i think its a 12AU7 i think. definitely has a 12 lol.

now i heard swapping out the sovtek tube will make the hissy fuzzy go away and would make a world of a difference in sound. i am thinking of doing that but how do i know what kind of preamp tube to get. I don't want to buy the wrong one.lol i just want that muddy hissy tone to be gone.
#2
AFAIK, all of the V-Series amps come stock with Groove Tubes/rebranded Sovtek 12AX7 tubes. To me, they're decent, but when I have to replace mine, I'm going with either Tungsol or JJ.

If you're going to replace one tube, you probably should replace them all so you don't have tubes with different ages. Eurotubes has a bunch of kits available for the different V-Series amps depending on what you want from the amp. Doug's Tubes and The Tube Store would also be able to build a matching set for you to fit your needs. A full retube for a 30 watt amp would probably run in the area of $60-70.
#3
what kind though cause im planning on ordering a pair from musicians friend? but there soo many and im not sure which will fit in my amp. does it have to be a 12AX7?