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Re: [Amps] 813's

To: Tom Osborne <>, "" <>
Subject: Re: [Amps] 813's
From: "Fuqua, Bill L" <>
Date: Tue, 22 Dec 2015 18:15:46 +0000
List-post: <">>
  Graphite is always messy, I have gotten it on hands clothes and it is hard to 
wash out.
I think perhaps they should not have earned such a reputation. I believe the 
problem stems from the
fact that most 813 amplifiers in the early days had untuned inputs and that 
they were pushed
harder than they should have been. Mind you these tubes in triode connection 
are about like 572B's.
They have even less plate dissipation than 572B's but I suspect the idea of 
pushing them to
2kW PEP plate input was just too much. Also, most used 813's I have gotten had 
very little
emission left. That is an indication that they were used beyond the point where 
if pushed to
get full gallon output they were probably producing a very dirty signal. I 
think if you use
a good pair, with tuned input and don't try to push them too hard they will be 
just fine. Treat them
as if they were a pair of 575B's. 
Bill wa4lav

From: Amps [] on behalf of Tom Osborne 
Sent: Monday, December 21, 2015 1:57 PM
Subject: [Amps] 813's

Why are 813 tubes considered 'dirty'?

I have an old amp in the attic I haven't used for a long time that has a
pair of 813's in it  I have read somewhere that they are a very 'dirty'
tube.  I'd assume that means lots of spurs or something.

Just wonder why that would be.  73
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