> I have seen designs for using such directly-heated cathode
> which simply attach the cathode common return to one of
> the filament
> connections. (The filament connections have multiple RF
> capacitors between them, and to ground.)
> What are the arguments for and against each of these
> approaches to
> providing the "cathode return"?
There is no cookie-cutter answer.
Depending on filament voltage and other operating/bias
voltages, you can get varying amounts of 60 cycle AC on the
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