On Jan 19, 2005, at 8:07 AM, Harold B. Mandel wrote:
Dear Steve,
Neutralization of tetrodes provides a better match between
the driver and Power Amplifier, and also serves to protect
the PA from deleterious oscillations.
With the cost of a replacement tetrode weighed against
the cost of materials, (inductor, capacitors, etc) of a
neutralization circuit it almost seems effective to
incorporate it in the design.
Amen, Hal. After consulting a number of "amplifier experts" about my
original 4cx5000A project -- a.k.a. Plywood Box #1), I was told that
neutralization was not necessary with a Cag (feedback-C) of "only" 1pF.
and a 450-ohm grid termination. This turned out to not be the case,
so I retrofitted a Bruene neutralization bridge, and revised my
"experts" list.
cheers
Hal Mandel
W4HBM
If the control grid were swamped in the 50 to 200 ohm range, and
the
Screen grid was made the shielding element (assume DC ground, and
cathode
and grid float DC), did you still experience instabilities such
that
neutralization was required ?
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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