[Amps] triode vs tetrode

[Jim Thomson]

Date: Mon, 5 Dec 2016 19:04:24 -0600
From: Mike Waters <mikewate at gmail.com>
To: Fern Rivard <crc at cyberlink.ca>
Cc: "amps at contesting.com" <amps at contesting.com>, Joe <nss at mwt.net>
Subject: Re: [Amps] triode vs tetrode

If that's the amp design I'm thinking about (4CX250B), it's a terrible
design. It was notorious for splatter and distortion.

With 813s, maybe it was OK.

73, Mike
www.w0btu.com

On Mon, Dec 5, 2016 at 6:54 PM, Fern Rivard <crc at cyberlink.ca> wrote:

> A better way yet is to go G2DAF

## several  4 x  4CX-250B amps were built locally in the 70s... all in G2DAF
format.  The trick in getting the IMD tamed was that screen circuit.  The precise
value of screen cap was required, or it went all to hell.   I still have my old
2 x 4-400A  G2DAF amp, recently modified to include 160M.   It uses
a  200 ohm non inductive resistor in the input with a 1:4 un-un.  Nobody
can hear the difference between it and my 3-500Z amps.  Again the screen
circuit has to be dead on perfect.  A fellow in W7 land, 22 miles away from me,
also has a 2 x 4-400  G2DAF amp. I dont hear any splatter on his signal, when
tuned off freq. 

##  I would not recommend the G2DAF  config however.   Its difficult  to make it
optimized correctly.  If you have  4-400s, or  4-1000s, its easier to just bond the grid + screen to the
chassis.   Another old fellow, a few miles north of me, used a 4-1000 in G2DAF. 
The 6x4 rectifiers were replaced with SS devices. It ran just fine, no splatter off freq,
but it too, was a bitch to get optimized.   

##  On my 2 x 813 amp..and also my old 4 x 813 amp,  I ran it as a high mu triode, and just
bonded the grid + screen to the chassis.    1.1 kw pep out of the 2 holer version. 

Jim  VE7RF