tube replacement for bat vk60

I just bought a pair of bat vk60 monos on audiogon and i got a crackling tube on one side . where is the best place to get replacement tubes . and do i have to buy the same tubes?
I would not recommend rolling tubes with the BATs. Call BAT and order through them. They give the best tube warranty I know of and do not bullshit. If I am not mistaken, their prices are not out of line.
Probably is one of the power tubes. I replaced mine and crackling disappeared.
Try cleaning the tube pins with pure electricians alcohal and/or fine cloth sandpaper (the name of it slips my mind now) before changing tubes. I have eliminated "rustling" in signal tubes by cleaning them well, plus thay sound a lot better.