#1
I have a Bugera 333xl head with 4 Bugera EL34 powertubes in it. I am thinking of buying a set like these: http://www.thomann.de/gb/tad_jj_el34_roehre_quartett.htm.

I plan on replacing the whole lot just so I can improve my tone a little bit (because ive heard the Bugera tubes suck). My question is: Do I need to rebias if I were to replace my stock Bugera tubes with that set?
Main Rig
ESP LTD MH-350NT
Korg Pitchblack > Digitech Bad Monkey
Peavey 6505+ 112 w/ 2x12 (Celestion Vintage 30 and WGS Veteran 30)
[Effects Loop] Boss GE-7 > Boss CE-5 > TC Electronic Flashback
#2
Yes, tubes are generally sold as matched sets but still need the bias set.
#3
Unless you get tubes with the same voltage rating as your old tubes, you should rebias.
Hi, I'm Peter