A DC filament has a varying grid to filament voltage along its length
and so has uneven cathode to plate current along its length. Thus
in theory, one end runs out of emission life faster than the other.
----- Original Message -----
From: "Randall D. DuCharme" <randyd@specent.com>
To: <amps@contesting.com>
Sent: Tuesday, October 31, 2000 7:37 PM
Subject: [AMPS] DC Filaments???
>
> Greetings,
>
> I was toying with the idea of running the filaments DC in an 813
> amplifier I'm starting. I was just told today that if I did that I'd
> have to reverse the polarity on the tubes periodically or suffer
> shortened filament life. Is there any truth to this? Is this something
> unique to the 813, something in common with all thoriated-tungsten
> types, or some sort of strange Halloween prank? I've never heard of
> this.
>
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