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6L6

Vacuum tube

Field	Value
image	[[File:Tube 6L6 Sylvania.jpg	190x502px]]
caption	A 6L6 tube manufactured by Sylvania
classification	Beam power tetrode
service	Class-A amplifier, class-B amplifier, class-AB amplifier, (audio amplifiers)
height_in	4.25
diameter_in	1.438
weight_lbs
cathode_type	Indirectly heated
heater_voltage	6.3
heater_current	900 mA
max_dissipation	30
max_voltage	500
Specification listed is for type 6L6-GC
pinout	[[File:BPT Pinout.png	thumb	left	125px	The 6L6 Pinout, metal versions had the shell connected to pin 1]]
class_a_anode_voltage	350 V
class_a_anode_current	54 mA
class_a_screen_voltage	250 V
class_a_bias_voltage	−18 V
class_a_anode_resistance	5 kOhms
class_ab_power_output	55 W
class_ab_anode_resistance	5.6 kOhms
class_ab_anode_voltage	450 V
class_ab_anode_current	2*54 mA
class_ab_screen_voltage	400 V
class_ab_bias_voltage	−37 V
reference	Essential Characteristics, General Electric, 1973

Specification listed is for type 6L6-GC

Pin 1 – n.c

Pin 2 – Heater

Pin 3 – Anode (Plate)

Pin 4 – Grid 2 (Screen)

Pin 5 – Grid 1 (control)

Pin 6 – n.c

Pin 7 – Heater

Pin 8 – Cathode & beam-forming plates

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. The 6L6 is a beam tetrode that utilizes formation of a low potential space charge region between the anode and screen grid to return anode secondary emission 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 (Isaac Shoenberg, Cabot Bull and Sidney Rodda) 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. Around one thousand of the N40 output tetrodes were produced, but MOV (Marconi-Osram Valve) company, under the joint ownership of EMI and GEC, considered the design too difficult to manufacture due to the need for good alignment of the grid wires. As MOV had a design-share agreement with RCA of America, the design was passed to that company.

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 was Micanol.

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.

Characteristics

Improved substitute

5881

Similar tubes

6P3S (6П3С)
6P3S-E (6П3С-E)
7027a
6BG6

References

J. F. Dreyer Jr., [https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1936-04.pdf "The Beam Power Output Tube"], New York: McGraw-Hill, ''Electronics'', April 1936, pp. 18 - 21, 35
RCA Manufacturing Co. Inc., [https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1936-05.pdf "Here is the New RCA 6L6 Beam Power Amplifier"], New York: McGraw-Hill, ''Electronics'', May 1936, back cover
Schoenberg, Rodda, Bull, [https://patents.google.com/patent/GB423932A/en?oq=gb423932a ''Improvements in and relating to thermionic valves''], GB patent 423,932, published Feb. 1935
Schoenberg, Rodda, Bull, [https://patents.google.com/patent/US2113801A/ ''Electron discharge device and circuits therefor''], US patent 2,113,801 published Apr. 1938
Editors, [https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1935-02.pdf "New Output Tetrode"], New York: McGraw-Hill, ''Electronics'', Feb. 1935, p. 65
K. R. Thrower, ''British Radio Valves The Classic Years: 1926-1946'', Reading, UK: Speedwell, 2009, pp. 125 - 126
O.H. Schade, [https://worldradiohistory.com/Archive-IRE/30s/IRE-1938-02.pdf "Beam Power Tubes"] ''Proc. I.R.E.'', Vol. 26, No. 2, Feb. 1938, p. 153
Editors, [https://worldradiohistory.com/Archive-Radio-Engineering/30s/1935/Radio-Engineering-1935-04.pdf "Metal Tubes for Receivers"], ''Radio Engineering'', April 1935, pp. 18 - 19
Metcalf, Beggs, [https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1935-05.pdf "All-metal receiving tubes, the manufacturing technique"], New York: McGraw-Hill, ''Electronics'', May 1935, pp. 149 - 151
RCA, [https://frank.pocnet.net/sheets/021/6/6L6.pdf RCA 6L6 Beam Power Amplifier], RCA Manufacturing Co., Inc.
Wholesale Radio Service Co., [https://worldradiohistory.com/Archive-Catalogs/Lafayette-Catalogs/Lafayette-1939-76.pdf Lafayette catalog no. 76], New York: Lafayette Radio Corp., 1939, pp. 38, 90, 96
L. C. Hollands, [https://worldradiohistory.com/Archive-Electronics/30s/Electronics-1939-03.pdf "Circuit Design Related to Tube Performance"], New York: McGraw-Hill, ''Electronics'', Mar. 1939, pp. 18 - 20
Editors, [https://worldradiohistory.com/Archive-Electronics/40s/Electronics-1940-01.pdf "The Electron Art" "Ultra-High Frequency Oscillation with the Beam Tube"], New York: McGraw-Hill, ''Electronics'', Jan. 1940, p. 69

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