~5F1 with KT66 power tube...speaker magnet effect on pwr tube?

[leevc5]

Back with another dilemma. Built a 5F2H with a 5F1 preamp section. The amp sounds spectacular....that is until I put it in the cabinet loaded with an Eminence Legend 12" speaker that has a big magnet. The amp as I said sounds good away from the speaker but when in the cabinet with the KT66 a few inches from the speaker magnet I get all kinds of weird humming noises. The noise gets more intense as the KT66 gets closer to the magnet so am taking a wild guess that the magnet is causing something to go wrong somewhere inside the tube.
Anyone know anything about this phenomenon?
Is there someway to effectively shield the tube(tried a sheet of aluminum and no help)?
Would really like to keep the big Champ set up have built.

[sluckey]

You can't shield a magnetic field with a nonmagnetic material such as aluminum. You may as well just use a sheet of glass. You can try a piece of steel on the chassis between the tube and the speaker. Or you can try shielding the magnetic field at the speaker. Do a google search for "speaker magnetic shield" for some ideas.

[PRR]

Magnetic shields usually have to be "all around". A flat sheet makes very little difference, the flux fringes around the edges.

I have not had trouble with magnets near tubes. If you do, you may have to move something.

[Willabe]

I had a problem with a tweed Deluxe.

I put in a big ceramic 12" speaker and the magnet was very close to 1 of the 6V6's, it lit up 1 of the 6V6's like a light bulb. 

So I made a new baffle board, shifted the speaker a couple of inches down and over/away from the power tubes, worked fine then. I moved it as much as I could in the little Deluxe cab.

[sluckey]

Put a steel bean can over the tube to see if shielding the tube will help. If no help you'll probably need to pursue shielding the speaker. Or use a bigger cab.