I'm fitting an oversize output transformer in an existing amp that had a bad one. I moved it to the edge of the chassis, even overhanging a bit, and that left about 3/4 inch from the open-style output transformer's windings to the last EL34. So I put thin steel bell-ends on the transformer, figuring that would protect it a bit from radiant and convection heat, maybe shield the tube from the magnetism a bit too, and the inside of the metal bell end has a fiber (like cardboard gasket material) electrical insulator inside which is also a bit of a heat insulator too). So that left only about 1/4 inch between the last EL34 and the output transformer. So I added a thin shiny aluminum shield/reflector between the tube and the transformer, spaced about 1/16" from the transformer. But now that's REALLY close to the tube.
Will an oversize output transformer leak much magnetic field outside its frame? I know output tubes sometimes have trouble from being too close to a speaker magnet (and the heat's not good for the speaker either). I'm not worried about the heat affecting the transformer now, it's protected acceptabley now. But will there be enough magnetic field from an output transformer to affect the tube's performance? I realize any effect drops quickly with distance, so the best solution is to just move it, but then I will have to make a new larger cabinet.
Will an oversize output transformer leak much magnetic field outside its frame? I know output tubes sometimes have trouble from being too close to a speaker magnet (and the heat's not good for the speaker either). I'm not worried about the heat affecting the transformer now, it's protected acceptabley now. But will there be enough magnetic field from an output transformer to affect the tube's performance? I realize any effect drops quickly with distance, so the best solution is to just move it, but then I will have to make a new larger cabinet.
I don't see a problem with stray magnetic field, the valves are not that much affected by them anyway. CRT now that's a different matter. They are as the magnetic field bends the electron flow and produces colour impurities on the final anode, (TV screen).
The main danger could be your shiny shield near the EL34. It will reflect anode heat back into the valve.
I let the transformer hang over the edge of the chassis a bit, will make a new cabinet, it's done, and I'll post a pic.
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