6L6 is the designator for a beam power tube introduced by

Radio Corporation of America 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 ...

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, ''Electronics'', April 1936, pp. 18 - 21, 35 The 6L6 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 formation of 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. This ...

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 emi ...

electrons to the anode and offers significant performance improvements over power pentodes. The 6L6 was the first successful beam power tube marketed. In the 21st century, variants of the 6L6 are manufactured and used in some high fidelity audio amplifiers and musical instrument amplifiers.

History

In the UK, three engineers at

EMI EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British transnational conglomerate founded in March 1931 in London. At the time of its break-up in 201 ...

(

Isaac Shoenberg Sir Isaac Shoenberg (1 March 1880 – 25 January 1963) was a British electronic engineer born in Belarus who was best known for his role in the history of television. He was the head of the EMI research team that developed the 405-line (Marconi-EM ...

Cabot Bull Cabot may refer to: Businesses * Cabot Corporation, an American chemicals company * Cabot Creamery, an American dairy cooperative Fictional characters * Alexandra Cabot, in the ''Law & Order'' universe * Leigh Cabot, from Stephen King's 1983 n ...

and

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) had developed and filed patents in 1933 and 1934 on an output tetrode that utilized novel electrode structures to form electron beams to create a dense space charge region between the anode and screen grid to return anode secondary electrons to the anode. The new tube offered improved performance compared to a similar power pentode and was introduced at the Physical and Optical Societies' Exhibition in January 1935 as the Marconi N40.Editors
"New Output Tetrode"
New York: McGraw-Hill, ''Electronics'', Feb. 1935, p. 65 Around one thousand of the N40 output tetrodes were produced, but MOV (

Marconi-Osram Valve M-OV (Marconi-Osram Valve Company) was a British manufacturer of thermionic valves (vacuum tubes). It was a subsidiary of the (British) General Electric Company Ltd. The company was founded in 1919, when the valve making interests of GEC (Osra ...

) company, under the joint ownership of

and GEC, considered the design too difficult to manufacture due to the need for good alignment of the grid wires.K. R. Thrower, ''British Radio Valves The Classic Years: 1926-1946'', Reading, UK: Speedwell, 2009, pp. 125 - 126 As MOV had a design-share agreement with

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 ...

of America, the design was passed to that company. Beam Pentode Cross Section

The metal tube technology utilized for the 6L6 had been developed by General Electric and introduced in April 1935, with RCA manufacturing the metal envelope tubes for GE at that time. Some of the advantages of metal tube construction over glass envelope tubes were smaller size, ruggedness, electromagnetic shielding and smaller interelectrode capacitance. The 6L6 incorporated an

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base, which had been introduced with the GE metal tubes. The 6L6 was rated for 3.5 watts screen power dissipation and 24 watts combined plate and screen dissipation. The 6L6 and variants of it became popular for use in public address amplifiers, musical instrument amplifiers, radio frequency applications and audio stages of radio transmitters. The 6L6 family has had one of the longest active lifetimes of any electronic component, more than 80 years. As of 2021, variants of the 6L6 are manufactured in

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China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, and

Slovakia Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the s ...

Variations

The voltage and power ratings of the 6L6 series were gradually pushed upwards by such features as thicker plates, grids of larger diameter wire, grid cooling fins, ultra-black plate coatings and low loss materials for the base. Variants of the 6L6 included the 6L6G, 6L6GX, 6L6GA, 6L6GAY, 6L6GB, 5932/6L6WGA and the 6L6GC. All variants after the original 6L6 utilized glass envelopes. A "W" in the descriptor identified the tube as designed to withstand greater vibration and impact. A "Y" in the descriptor indicated that the insulating material of the base wa
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Application

The high transconductance and high plate resistance of the 6L6 requires circuit design that incorporates topologies and components that smooth out the frequency response, suppress voltage transients and prevent spurious oscillation.L. C. Holland
"Circuit Design Related to Tube Performance"
New York: McGraw-Hill, ''Electronics'', Mar. 1939, pp. 18 - 20

Characteristics

Improved substitute

* 5881

Similar tubes

* 6P3S (6П3С) * 6P3S-E (6П3С-E) *

7027a 7 (seven) is the natural number following 6 and preceding 8. It is the only prime number preceding a cube. As an early prime number in the series of positive integers, the number seven has greatly symbolic associations in religion, mythology, s ...

References

External links

TDSL_Tube_data_[6L6
/nowiki>.html" ;"title="L6">TDSL Tube data [6L6
/nowiki>">L6">TDSL Tube data [6L6
/nowiki>
Electron Tube Data sheets
Several 6L6 datasheets from various manufacturers * {{cite web , url=http://www.amplifiedparts.com/sites/all/modules/custom/tech_corner/files/6l6gc_comparison_of_current_made_tubes.pdf , title=6L6GC Comparison of Current Made Tubes , type=PDF , author=Kurt Prange , access-date=2014-02-16 , archive-url=https://web.archive.org/web/20140221181448/http://www.amplifiedparts.com/sites/all/modules/custom/tech_corner/files/6l6gc_comparison_of_current_made_tubes.pdf , archive-date=2014-02-21 , url-status=dead
Reviews of 6L6 tubes
Vacuum tubes Guitar amplification tubes Telecommunications-related introductions in 1936