OK cheers, I just don't want to put those tubes in and have the amp blow up.

So in what situation would you need to bias an amp? Forgive me I don't fully understand biasing.

Also I only have 2 power tubes whereas the amp takes 4. Would it be ok to keep 2 stock power tubes in and use 2 new ones, as well as replacing all the preamp ones?
Last edited by Random3 at Mar 1, 2012,
The situation in which you have a different amp, or a strong desire to rewire the 6505 to have an adjustable bias. It can make the amp sound better but biasing isn't necessary or possible on a lot of (stock) modern amps.