Help with noisy power tube!

Hi-- I have a Jolida 502B and just installed a new quad of Svet 6550c's. When the power is on, I can hear one of the tubes making a faint, constant ringing/buzzing sound (like the sound of a lightbulb when you shake it and the filament vibrates), and I can only hear it if my ear is near the unit. The sound coming out of my speakers is fine, as far as I can tell. Is this something I should worry about? Thanks. d
I would not be concerned about little noises as the tubes warm up from being cold. But if it is constant after they are hot, try swapping the tubes around. It could be that the bias is way off. If the same tube is noisy, you should return the tube to where you got it and they should replace it. This is not normal. If they were a matched quad, they should give you a new set. You should also be careful not to burn your ear when it is close to the tubes.
I've owned many tube amps over the years and I own the Jolida in my bedroom system. It is fairly frequent to have some noises with power tubes. It's easier to hear if the unit doesn't enclose the tube or if the tube cage is relatively open. I suggest you let the unit warm up first since tubes do make a fair amount of noise warming up. Check your bias. If it is OK and after 30 minutes you can only hear the sound in a quiet room with your ear within 12" of the exposed tube I wouldn't worry too much. If they were only sold as a matched quad from stock tubes and not a hand selected and then matched quad you can decide if you want to take them back. If you paid for a hand selected AND matched quad, I'd take them back since during hand selection a slightly noisey tube should have been eliminated. BTW if you listen to a lot of rock or classical music with a lot of bass I would recomment KT-88's.