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Old 13th Jan 2019, 8:27 am   #56
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: 120W PP EL34 amplifier re-born.

"ali will not shield from magnetically induced hum." Thought it did? Was under the impression steel didn't as it can become magnetised. Seems I'm wrong - "the 'shield' needs to be of a material that has high permeability or low reluctance (they are reciprocal like resistance and conductance). The permeability of iron is .25 and the permeabilitu of aluminum is 1.25 x 10>-6. Nearly a million times less able to reduce magnetically induced hum."

This galling as I am pretty sure I read that ali was a good shield in a chapter on chassis building in toob amps. Oh well, you live and learn.

Andy.
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