[AMPS] neutralizing

[i4jmy@iol.it]

It's not a smart idea to neutralize a Gg amplifier because that 
configuration is inherently stable and doesn't require it. 
When a tube doesn't comply with the above statement and requires to be 
neutralized also in a Gg, the plain solution is to change the tube to 
another type or to swap into a cathode driven configuration. 
Dealing (suffering) with a neutralizing circuit is worth when a voltage 
drive is possible and the power gain becomes much higher. 

73,
Mauri I4JMY


>  I've known about neutralizing amps for many years, and repaired many 
of
> them for the gov't but I don't recall ever seeing a GG amp 
neutralized.
> Since the plate and cathode ckts. are in phase with each other, and 
180
> degrees out of phase with the grid, it follows that , directly from 
plate to
> ground one would need a phase inversion. this of course could be done 
with a
> coil and a cap, but it doesn't seem to me that the feedback would 
remain
> exactly what it needs to be on all bands in a bandswitching amp. in 
the old
> days, with grid driven amps, and single band, it seemed to work well, 
but
> today it's a different story. all this is what I learned over the 
years, and
> of course I could be slightly off base or have forgotten my basics
(it's been
> a looong time) and I was out of the game for nearly 30 years!!!I've 
recently
> repaired some sb200's and one sb220 and the owners are happy with them
(and
> the amps aren't neutralized), so maybe I haven't totally lost touch 
with
> reality.Any comments?? (I can still learn!!)       carl / kz5ca



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