[AMRadio] Grounded grid amp

[John Coleman]

I remember when I was a teen.  I had a pair of 813s in a final and the rig
was some surplus thing made by FEDERAL.  It had no modulator. So I wire up a
pair of 1625s in the triode connection zero bias configuration as the RCA
book said to do on 807s.  The original supply was only 450 volts to the
final and the modulators.  I think the power out of the 813s was only 25
watts.  But as time went by I got bigger supplies.  And went as high as 1800
volts on the 813s and the 1625s.  Those little bottles actually worked
pretty well even at that high voltage but you had to limit the bass and
never say fourrrrrrrrrr! Cause there would be lots of spitten and sparkin in
the glass!
John

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of David Folger
Sent: Wednesday, January 26, 2011 11:03 AM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] Grounded grid amp

Another option would be 2 to 4 6DQ5's. The 6DQ5 is cheap and easy to come
by. Higher plate dissipation than a 6AG7.

There are designs on the net. I would think you could get about 100W out on
AM with four of them as they have about 25W dissipation each.

Other sweep tubes would work also, but most are more expensive.

Just don't get carried away and believe the specs from some of the '70s era
sweep tube linears. They were overrated and burned tubes like crazy with
crappy signals to boot.

--- On Wed, 1/26/11, Hiroki Kato <hirokik at aol.com> wrote:

From: Hiroki Kato <hirokik at aol.com>
Subject: [AMRadio] Grounded grid amp
To: "Discussion of AM Radio in the Amateur Service"
<amradio at mailman.qth.net>
Date: Wednesday, January 26, 2011, 7:54 AM

Many years (decades) ago I saw a small amp using 5 x 6AG7 in parallel using
grounded grid. Very simple and elegant design. Perhaps it was in QST but I
may be mistaken. Anyone has any info? I would like to build a 50-100 watts
amp to boost an ARC 5.

Hiroki AH6CY
> 
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