Will Matney wrote:
> What I looked at in the schematic didn't make one lick of sense
> to put a cathode choke to ground on a grid driven amp,
> then place a shunt resistor across the choke
> (especially that high of value).
> The resistor wouldn't serve any purpose unless the choke opened.
> And if it did, you'd really be better off not to have the resistor
> so the tube would not conduct at all.
> Also, the choke isn't needed as there's NO RF there to block
> from ground. He also put a RF choke across the attenuator resistor
> going to the control grid.
> That don't make sense to me. I would think you would use two
> non-inductive resistors. (Rich will jump me for calling them
that). > He also has a choke in series with one of the attenuators
resistors
> going to ground which would raise the impedance there too.
>
> All I've ever seen here, for an attenuator, is a couple of
> non-inductive resistors.
>
> Why put a choke in series with the screen lead? All that's needed
> is a bypass cap at the tube socket pin. Here, the cap is on the
> other side of the choke where it's shouldn't be.
> Last, there's a 0.001 bypass cap hooked right from the control grid
> to ground on the wrong side of the RF blocking choke.
> The RF will go to ground and not to the tube!
>
> Am I missing something about this?
Is it possible that these chokes and capacitors you mention are pars
in a peaking circuit, to push the frequency response of the amplifier?
That would explain the high value parallel resistor (limiting the Q)
and the cap on the tube side of the grid choke (to form part of a
resonance, not a bypass). I am afraid I have lost the original link
to the schematic, so I can't easily look if this explanation is
reasonable or silly.
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