[gdrfk1990]

Do they have to be rebiased or can I just pop new ones in and if I am changing them are there any suggestions on switching them up.?? Thanks in advance
Eric

[tigerstrat]

This info is readily available all over the internet: re-bias the amp after changing power tubes; preamp tubes don't require bias adjustments.

[sants]

If you get tubes that are matched some people will tell you the amp doesn't have to biased because they should be drawing the same current. However, I always have my amps rebiased when replacing tubes unless the amp is fixed bias. Any decent amp tech should be able to bias your amp in 15 minutes.

[modz]

I re bias my amps when changing power tubes as well.
http://www.guitargeek.com/chat/showthread.php?t=81368