The Illustrious 6L6 tube (Part 4)

Brian Carling bry at MNSINC.COM
Mon Sep 22 21:24:49 EDT 1997

It is estimated that more than 2 million tube guitar amps exist in the
world today. Of that number, probably more than 40% use push-pull
6L6s. To claim that this market will soon dry up and be replaced by
transistors is simply prevaricative. Although no 6L6 type is being
produced in America or Europe at the present time, there are a few
popular ones from Russia and China which own the market. The Shuguang
types, including a new 6L6GC with a blue glass envelope, are
consistent sellers; and although they are very clean-sounding tubes,
the Russian-made 5881s are Soldano's favorites and are used widely.
They will likely be available for years, if not decades, to come. Add
in the soon-to-come Svetlana 5881 and a rumored 6L6GC-"STR" which may
be produced in California soon, and the 6L6 looks good for another 60

The British Connection
In England in 1931, J.H. Owens Harries discovered that if the electron
flow in a tetrode was confined to beams, and that the distance from
screen grid to plate was kept at a critical distance, secondary
emission from the plate would be suppressed, just as in a pentode1,3.
This discovery enabled the British General Electric Co. (GEC,
unrelated to the American General Electric) to bring out a sensitive,
high-power output tube without infringing on the pentode patents held
by Philips and Mullard. GEC then came out with a series of beam
tetrodes, with their most famous being the KT66. KT stood for
"Kinkless Tetrode" -p; since it eliminated the kink in the transfer
curve that happened with regular tetrodes. The KT66 was meant to be a
plug-in replacement for the 6L6, but had superior characteristics. It
was introduced in 1937.

Due to: the head start the British had in developing component-type
high fidelity systems, the transfer of British RADAR technology to
American during WW II, and the common language, Americans in the late
1940s looked to England for ideas in hi-fi design. Williamson's
seminal Wireless World articles gave British hi-fi a tremendous boost
in America. The marketing efforts of the British Industries Corp
(B.I.C.) brought the best of British hi-fi components to America
during the 1950s. The net result of this was the inclusion of
"foreign" tubes, such as the KT66, KT88, EL34, GZ-34, etc. into
American hi-fi and even guitar amp designs.

1 -p; Harries, Secondary Electron Radiation, Electronics, Sept. 1944.
2 -p; Schade, O.H., Proc. of the IRE, Feb. 1938. 3 -p; Harries,
British patents 380,429 and 385,968, 1931. and Wireless Eng., vol. 13,
pp. 190-199, April 1936.

See also:

Bry's Tube Data Pages:


The Ampage tube data page:
Svetlana's tube data:
Vacuum Tube Valley: An interesting
scientific essay on why tubes sound better:

Enjoy!! 73 to all and special thaks to Eric Barbour for the great

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