[Top] [All Lists]

[Amps] Grid neutralized triodes

To: Amplifiers <>
Subject: [Amps] Grid neutralized triodes
From: "Fuqua, William L." <>
Date: Sat, 15 Jan 2022 17:11:32 +0000
List-post: <>
  Many years ago we discussed plate and grid neutralized triode amplifiers.
Just about all common cathode triode HF power amplifiers used HV split stator
plate capacitors rather than lower voltage ones on the grid.
  Well, I had come up with an complicated explanation and realized now that it 
was wrong.
I believe the reason that it was so commonly used had to do with imbalance as 
the capacitance
was varied.
  If you plate neutralize cancel out the plate grid capacitance which also 
eliminates most of the
plate to cathode capacitance.  So, as you go from max to minimum capacitance 
there is little imbalance.
And it is unlikely that the amp will go into oscillation when at the extremes 
of the tuning range.
  However, if the split stator is on the grid one half has the grid cathode 
capacitance shunting it and the
other has no additional shunt capacitance.
   The Johnson Courier amplifier has a split stator grid circuit, two parallel 
811A tubes and a PI network
output. However, a closer look will reveal a shunt capacitor on the stator that 
is connected to the neutralization
   Look at the BC-375, it has a very complex neutralization method.
Also, although a bit risky, some higher power amplifiers published in the GE 
notes have MB-150 multiband split
stator tuners on the grids and PI network outputs. I say a bit risky because 
there is not a shunt cap on one stator.
  That being said, I wish I had time to experiment with some amplifiers and put 
some of my old big triodes to work.

Bill wa4lav
Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>
  • [Amps] Grid neutralized triodes, Fuqua, William L. <=