This might give you a clue, but not the full answer: a lamp manufacturer
published a treatise on this subject and concluded that ac was better for life
expectancy. Something to do with migration of electrons from the surface of
the filament, with dc it was all one way and eventually led to break down; with
ac there was little net migration. They showed electron micro photos. I have
a mental picture of the lamp brochure, but can't remember who.
David
G3UNA
>
> From: eran <erniaba@netvision.net.il>
> Date: 2008/02/13 Wed PM 12:11:51 GMT
> To: amps@contesting.com
> Subject: [Amps] filament supply D.C or A.C
>
> Looking for reliable information regarding filament supply to amplifier
> tubes. What are the pros and cons for D.C or A.C volts.
>
> Thanks and 73s Eran
> 4X1MO
>
>
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> 12:21 PM
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