>
>Rich says;
>
>>Please name a (not G-G) Collins amplifier that used AB2 instead of AB1.
>
>Now unfortunately, I don't know the number. But it's the 45kW amp described
>by Bruene in the Proc IRE article pp1760 - 1765 December 1956.
>
>>The constant current curves prove why this is generally the case
>
>For some tubes only - not all. You are still generalising. Try the 4CX5000A.
>
? ok. please see http://www.vcnet.com/measures/8170.JPEG for the
requisite constant-current curves.
In the region below the 0-volt grid line, the curves are pretty straight
at low anode potentials - indicating that linearity is fairly good.
However, at the grid's +50-volt line, the anode I curves bend. Deviation
from a straight line indicates distortion. Furthermore, the peak grid
current is c. 0.15a at 50v. Thus, the grid looks like 330-ohms. Since
the typical grid terminating resistor is 450 ohms, instead of the exciter
seeing a 50-ohm load through the 1:9 transformer, it now sees a 191/9
-ohm load. A 22-ohm load is hardly good-news for modern solid-state
50-ohm radios. And what did running this amount of grid current "buy" in
terms of power? A fraction of an S-unit at the receiving end -- plus
whatever splatter happens to be generated.
.
>Some tubes are designed for no grid current.
All tetrodes except the 4CX1000A are designed to handle grid current.
>Not all tubes. However, your
>comments are getting more specific, so we are getting convergence between
>our points of view.
>
cheers, Peter
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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