What is Kinkless Tetrode
From martin–(at)–houl.bri.hp.com Mon Feb 12 11:43:24 CST 1996
From: martin–(at)–ri.hp.com (Martin Ackroyd)
Newsgroups: rec.audio.tubes
Subject: Re: What is a Kinkless Tetrode?
Date: 12 Feb 1996 08:43:10 GMT
Reply-To: martin–(at)–houl.bri.hp.com
b.stac–(at)–enie.com wrote:
: I’ve heard that the “KT” in KT-66, KT-77, and KT-88 stands for
: Kinkless Tetrode, and that this is somehow different from a
: beam power tube.
: Is there any real difference? Who came up with this idea?
There is no difference. Same thing. Here’s the story as I know it…
In the 1930’s, Mullard had the patents on the pentode, so other
firmes had to pay royalties. EMI invented the beam tetrode as a
way to avoid paying the pentode royalties. But good ole EMI
chose not to exploit it commercially. They had a patent sharing
agreement with RCA, who immediately saw the potential and produced
the 6L6.
GEC [the British General Electric company – nothing to do with American
GE] then decided to make an equivalent to the 6L6 and, in around 1937,
produced the KT66, as a plug in replacement for the 6L6
GEC got very enthusiastic about ‘kinkless tetrodes’ and used the
principle to produce rf valves [KTZ63, KTW63] that were alternatives
to the rf pentodes 6J7, 6K7.
My dad was working at GEC on radio design at the time and the above
is how he told me the story.
‘Kinkless’ just means the anode characteristic does not have a negative-slope
region [‘kink’] like the original rf tetrodes from the early 30’s had,
caused by secondary electrons emitted from the anode, arriving at the
screen grid when the screen grid is more positive than the anode.
[eg like in an output tube with big anode voltage swings].
.
Using a suppressor grid [making the tube into a pentode] is one way
to make sure secondary emission from the anode does not give the kink.
Using beam forming electrodes plus careful alignment of electrode structures
is another way.
To repeat: “Kinkless Ttetrode” = “Beam power tube”.
Same thing. No difference.
—
Martin A.
—————————————————-
From audioen–(at)–vpal.svpal.org Mon Feb 12 12:26:14 CST 1996
From: audioen–(at)–vpal.svpal.org (Scott Frankland)
Newsgroups: rec.audio.tubes
Subject: Re: What is a Kinkless Tetrode?
Date: 12 Feb 1996 17:34:18 GMT
Distribution: world
b.stac–(at)–enie.com wrote:
: I’ve heard that the “KT” in KT-66, KT-77, and KT-88 stands for
: Kinkless Tetrode, and that this is somehow different from a
: beam power tube.
: Is there any real difference? Who came up with this idea?
The kinkless tetrode is a beam power tube [1]. It differs from the
ordinary tetrode in the same way that other beam tubes do; i.e., it
provides a virtual suppressor [2]. Beam tubes differ from other beam tubes
mainly in the manner in which the electron stream is formed; i.e., in the
shape and position of the beam formers [3]. The 6L6 was the first beam
tube [3].
[1] M.O. Valve Co. Ltd. tube specification, London, England.
[2] O.H. Schade, “Beam Power Tubes”, *Proc. IRE* Feb. 1938, pp. 162–176.
[3] Richard F. Shea, Editor-in Chief, *Amplifier Handbook*, McGraw-Hill,
NY, 1966.
~SF~
