[Amps] cathode return?

[R L Measures]

On Jun 25, 2006, at 2:33 PM, gdaught6 at stanford.edu wrote:

> Gentlemen,
>
> I am in the throes of building a grid-driven amplifier using a tube
> with a thoriated-tungsten filament that has a rather unusual filament
> voltage, and my filament transformer has no center tap.
>
> I know about the "trick" of using a smallish center-tapped
> transformer to provide the cathode return, where the transformer
> needs to be rated for the DC cathode/anode current.  I am prepared to
> do this, but...
>
> I have seen designs for using such directly-heated cathode tubes
> which simply attach the cathode common return to one of the filament
> connections.  (The filament connections have multiple RF bypass
> capacitors between them, and to ground.)
>
> What are the arguments for and against each of these approaches to  
> providing the "cathode return"?

Constant 60Hz signal in series with grid-bias supply.

>
> 73,
>
>    George T. Daughters, K6GT
>
>
>
>
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R L MEASURES, AG6K. 805-386-3734
r at somis.org