12AT7 vs. 12AT7WA

[Jordan Arndt]

Chris Trask wrote:
>
>         In general, the "A" dsignated a tube series where the filament has
> a contolled warm-up time.  These were made to accomodate equipment where
> the filaments were wired in series, such as a transformerless TV set.
>
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The "A" Series are also recommended in circuits which require stabilty,
as the Controlled Heater Warm-up uses a different filament alloy, which
has a different Ohms/Degree F ratio than standard filaments... 73 de
Jordan...

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