Rich said:
> For a tetrode, if the anode V increases, ZSAC increases. If the
>increase was due to a rise in mains-V, -- and the mains also powers the
>grid bias supply, the increase in ZSAC is somewhat countered by an
>increase in -V to the grid. Thus, in this case, an unregulated grid bias
>supply would provide a miniscule advantage.
If the tetrode has any Ra (plate resistance) at all, Ia is relatively
insensitive to Va. It is sensitive to Vg2, and my original comment was that if
Vg1 and Vg2 are unstabilised so that they both float with changes in mains, then
the zero signal plate current stays relatively constant. Which is pretty well
what Rich says, if different words. Guess we have agreement on that point.
Note I differentiate here between 'stabilise' and 'regulate'. Regulation is the
variation in voltage of a supply with changing load: stabilisation is variation
of the supply with changing input.
Zeners are best fed from constant current sources - it's just not always
possible!
73
Peter G3RZP
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