KT66 is the designator for a beam power tube introduced by Marconi-Osram Valve Co. Ltd. (M-OV) of

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

in 1937 and marketed for application as a power amplifier for audio frequencies and driver for radio frequencies.Editors
"The New Valves"
''Wireless World'', August 20th 1937, p. 178General Electric Co., Ltd.
"Osram Valves"
''Television and Short-Wave World'', Sept. 1939, p. 524 The KT66 is a

beam tetrode A beam tetrode, sometimes called a beam power tube, is a type of vacuum tube or thermionic valve that has two grids and forms the electron stream from the cathode into multiple partially collimated beams to produce a low potential space cha ...

that utilizes partially collimated electron beams to form a low potential

space charge Space charge is an interpretation of a collection of electric charges in which excess electric charge is treated as a continuum of charge distributed over a region of space (either a volume or an area) rather than distinct point-like charges. Thi ...

region between the anode and screen grid to return anode

secondary emission In particle physics, secondary emission is a phenomenon where primary incident particles of sufficient energy, when hitting a surface or passing through some material, induce the emission of secondary particles. The term often refers to the em ...

electrons to the anode and offers significant performance improvements over comparable power pentodes.Dreyer, J. F. Jr.
"The Beam Power Output Tube"
''Electronics'', Vol. 9, No. 4, April 1936, pp. 18 - 21, 35 In the 21st century, the KT66 is manufactured and used in some high fidelity audio amplifiers and musical instrument amplifiers.

Overview

Although the

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

6L6 6L6 is the designator for a beam power tube introduced by Radio Corporation of America in April 1936 and marketed for application as a power amplifier for audio frequencies.J. F. Dreyer Jr."The Beam Power Output Tube" New York: McGraw-Hill, ''Ele ...

of 1936 (the result of a license agreement between RCA and EMI) was the first successful beam power tube on the market, the KT66 of 1937 became almost equally famous, at least in Europe. Because the beam tetrode design eliminated the ''tetrode kink'' in the lower parts of the tetrode's voltage-current characteristic curves, M-OV marketed this tube family as the "KT" series, standing for ''kinkless tetrode''. The KT66 was one of the "International series" introduced in 1937. This series utilized the "American Octal" base and had characteristics equivalent to tubes by U.S. manufacturers. A number of different KT tubes were later marketed by M-OV. Some, but not all, were versions of existing American

tubes or European power

pentode A pentode is an electronic device having five electrodes. The term most commonly applies to a three-grid amplifying vacuum tube or thermionic valve that was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926. The pentode (called a ''trip ...

s, such as the KT66 (6L6GC similar), KT77 (EL34 and 6CA7 similar),

KT88 The KT88 is a beam tetrode/kinkless tetrode (hence "KT") vacuum tube for audio amplification. Features The KT88 fits a standard eight-pin octal socket and has similar pinout and applications as the 6L6 and EL34. Specifically designed for audio ...

(6550), and KT63 (6F6, pentode but almost identical characteristics). Sovtek kt66 power tetrode

The KT66 was very popular in European

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a tr ...

s and audio

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...

s. It was the standard output tube in the classic

Quad Quad as a word or prefix usually means 'four'. It may refer to: Government * Quadrilateral Security Dialogue, a strategic security dialogue between Australia, India, Japan, and the United States * Quadrilateral group, an informal group which inc ...

II (1952, a version of which is still being manufactured today) and in the LEAK Type 15 (1945) and TL/12 (1948), both among the earliest British hi-fi amplifiers. Because of their excellent electrical characteristics and overload tolerance, KT66s are preferred by some guitar players for use in

guitar amp A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which a ...

s in place of 6L6GC. However, the plate dissipation of the 6L6GC, at 30W, exceeds the KT66's 25W, and adjustment of the amplifier's

bias Bias is a disproportionate weight ''in favor of'' or ''against'' an idea or thing, usually in a way that is closed-minded, prejudicial, or unfair. Biases can be innate or learned. People may develop biases for or against an individual, a group ...

is necessary. M-OV ceased glass vacuum tube manufacturing in 1988; their old audio tube types became valuable collectibles. In 2004 original M-OV KT66 tubes (bearing the official "Genalex" marketing brand that M-OV used outside the UK), unused in original carton, sold for US$250. KT66 tubes continued to be manufactured at EkspoPUL in Saratov, Russia ( Genalex Gold Lion brand), JJ Electronicin Slovakia, and by Hengyang Electronics at former GuiguangRachel Zhang, Who was Guiguang? factory in Foshan city, southern China. Some modern Russian manufacture Sovtek KT66 tubes are actually 6L6GC tubes in a KT66 style bottle. While these tubes have the same pinout and minimum tolerances required of a KT66 tube, they do not have the performance characteristics of a true kinkless tetrode KT66 tube. By contrast the very latest Russian manufactured tubes (2012) not only carry the same internal electrode structure as the original KT66 (they now look the same) they also have the same rugged electrical characteristics and can withstand a high voltage on grid 2 comparable to the anode voltage rating, allowing greater power output afforded by higher voltage capability when run in ultralinear connection.

References

* Barbour, Eric. "History of the 6L6" in ''Vacuum Tube Valley'', issue 4 (1996), p. 3. * Schade, O. H. "Beam Power Tubes" in ''

Proceedings of the IRE The ''Proceedings of the IEEE'' is a monthly peer-reviewed scientific journal published by the Institute of Electrical and Electronics Engineers (IEEE). The journal focuses on electrical engineering and computer science. According to the ''Journa ...

'', February 1938. * Stokes, John. ''70 Years of Radio Tubes and Valves''. Vestal Press, NY, 1982. * Thrower, Keith. ''History of the British Radio Valve to 1940''. MMA International, 1982, p. 59.

External links

Several tube datasheets

TDSL_Tube_data[KT66
{{DEFAULTSORT:Kt66 Vacuum_tubes.html" ;"title="T66">TDSL Tube data[KT66
{{DEFAULTSORT:Kt66 Vacuum tubes">T66">TDSL Tube data[KT66
{{DEFAULTSORT:Kt66 Vacuum tubes Guitar amplification tubes Telecommunications-related introductions in 1937

Overview

See also

References

External links