re the ongoing debate,
> >Whenever grid current
> >flows in a grid driven amplifier, linearity is compromised.
>
> Rich, you keep saying that in such sweeping, all-inclusive terms.
> You may believe it most sincerely, but that still doesn't make it true.
my unsolicited $0.02 worth is... there are tubes where even a teensy
bit of grid current will result in compromised linearity. there are
tubes where a fair amount of grid current can be drawn, with no
compromise. it ain't grid current that's the defining
characteristic! it's the linearity! the "transfer characteristic"
should be a straight line. if it bends, then it ain't linear.
with many modern tetrodes, even those with handles, there is a serious
bend that occurs just about at 0 volts on the grid. the control
grids are really good at intercepting electrons on their way from the
cathode to the plate. if the grid starts grabbing a significant
amount, then linearity goes to pot. what is "significant"? it
depends on how much "to pot" you're willing to accept. if the 3d and
higher order products are legal, then maybe it's not so bad.
but it depends on the tube!
ok, maybe that was only a penny's worth.
73,
George T. Daughters, K6GT
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