I just recently put new JJ/Tesla Tubes in my Peavey Classic however I'm kind of disappointed. After I put the tubes in turned the amp on and started playing I noticed my tone sounded drastically different, in a bad way.

Does this mean I need to get the tubes biased? I know the Peavey Classic is a fixed bias amp, but couldn't the bias still be set fairly cold? Also how much should it cost to get it biased if necessary? If anybody has some advice on how to solve my problem then please reply, thanks.
Jackson DKMGT with semour duncan pickups
Peavey Classic 30 (upgraded speaker)
Digitech Digidelay
Ibanez TS9DX Turbo Tube Screamer
Dunlop wah
Boss DS-1
Rogue LX400 pro- 4 string bass
Rogue RB60 60 watt bass combo
If it's a fixed bias amp, then there's nothing you can do about it unless you want to mod your tube amp, which is not cheap and probably what the guy from Eurotubes would probably recommend, which is probably where you got your JJs from... Personally, I don't get why Eurotube is so trendy on this site, but whatever. I'm ranting.
Hi, I'm Peter
Your fixed bias amp can be rebiased either by changing the resistors that set your bias or adding trimmer pots in place of the resistors to create adj bias. I would think they would have selected the proper tubes to match your amp before shipping them but perhaps not. Call Eurotubes and see what they say.
It's a fine line between clever and stupid.