Do I need to have the bias of my 5150 checked ??

[Sly]

Please help me guys :

I have an old Peavey 5150 Mk1 amp since a year, I bought it from an american guy (it has a 110V power supply, I use a 110 to 220V 500 watts converter) and it is pretty awesome. I just bought a Bogner 2x12" cab which is killer. I use a Maxon OD-808 in front of the amp most of the time.

These days the amp does not seem to have as much gain as it used to have. So I think the tubes in there are old. The guy before me changed the tubes once.

I now want to get new preamp AND power tubes to have a completely new setup, and a tech told me that the following tubes should sound good and would match what I want to get from the amp (which is 90% of the time used for recordings) :
power : Sovtek 6L6WXT+
preamp : JJ ECC83S

Do you think I have to bring the amp to have the bias checked ? Or do I have to first install the new tubes, then check if something is wrong or not ?

 

[elmuchoescadawg]

Theres no bias adjust on the mark ones.

 

[guitarguru1969]

You can have the bias mod performed which I highly recommend. The heads are biased cold at the factory, why I don't know because the 2X12 versions are biased correctly at around 35ma plate current. The heads are biased near the lower teens causing fuzzy crossover distortion. I had the bias mod performed and put to the scope and it got out of the woods at the 35ma plus range. I now have mine set at 39ma plate current. It realy tightened up the lower end and added more clarity overall. The big plus is that the fuzz is gone!