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[AMPS] Re:Question: input Z on class AB gnd grid pair 4-400 ??

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Subject: [AMPS] Re:Question: input Z on class AB gnd grid pair 4-400 ??
From: Jan.E.Holm@telia.se (Jan.E.Holm@telia.se)
Date: Thu, 13 Jan 2000 08:07:15 +0100
With 100W drive and 3kV on a pair of 4-400´s it might
be a problem to get 1500 out, better run 4 kV on plates.
I have a 3 tube 4-400 amp 10 - 160m and it runs excelent.
After 20 years of service it still runs full output and
the tubes wasn´t even new back then, I run slightly less
then 4kV on them and they are GG. If you have the hardware
for a 3 tuber that´s the way to go.

73, Jim SM2EKM

PS: You can use the same tuned input as a SB-220 (or similar)
    uses and just tweak it.
--------------------------------
>  
> Greetings,
>  
> After digesting the material that I have collected and the responses
> from an earlier post (tnx, Skipp), I think the best way to go for my
> homebrew amp is to run the 4-400's in class AB grounded grid.
>  
> I have dug up a couple of construction articles.  One is from the  
>1982
> ARRL Handbook.  In chapter 6, it describes "An Economy 2-kW  
>Amplifier"
> that uses these tubes grounded grid.  It doesn't, however, have a  
>tuned
> input network.
>  
> I'd like to add one.  But before I do, I need to know what the  
>approx.
> input impedance is for a pair of 4-400's in grounded grid.  If it
> matters any, I plan to run 3000 ~ 3500v on the plates.
>  
> Thanks in advance!
>  
> 73,
> Charlie  N9CO
>  
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