6SN7

6SN7 is a dual triode vacuum tube, on an 8 pin octal base. Although the 6S-- series tubes are often metal cased, the 6SN7 is generally found only in a glass GT size envelope. The 6SN7 is basically two 6J5 triodes in one glass envelope.

History

Originally released in 1939 it was officially registered in 1941 as the glass-cased 6SN7GT. During World War II a 6SN7A was developed as a slightly improved version, then also a more rugged 6SN7W for military use.

With the advent of television the 6SN7 was well suited for use as a vertical-deflection amplifier. As screen sizes became larger, the tube started to have marginal voltage and power headroom. To address this, upgraded versions GTA (General Electric, 1950) and GTB (GE, 1954) were made with higher peak voltage and power ratings. The 6SN7GTA has anode dissipation uprated to 5.0 watts "design center rating". The 6SN7GTB is identical to the 6SN7GTA except for a controlled heater warmup time, for use in Television sets with 600 mA series heater strings.

The 6SN7 has a 6.3 V 600 mA heater/filament. The 12 volt filament equivalent is the 12SN7GT or 12SN7GTA. (12.6 V 300 mA filament) There was also a comparatively rare 8SN7 (8.4V@450mA filament intended for 450 mA series string TV sets)

Numerous other variations on the 6SN7 type have been offered over the years, including 7N7 (Sylvania 1940, loktal-base version), 5692 (RCA 1948, a super-premium version with guaranteed 10,000 hour lifetime), 12SX7 (RCA 1946, intended for use in 26-volt aircraft electronics), 1633 (RCA 1941, also for 26-V radios), 6042 (1951, another 1633 type), and 6180 (1952). American military designator for the 6SN7GA was VT-231, and the British called it CV1986 or CV1988. European designators include ECC32, 13D2 and B65. Each of the giant SAGE computer systems used hundreds of 5692s as flip-flops.

While often used as an audio amplifier in the 1940-1955 period, usually in the driver stages of power amps, the 6SN7 was also very popular in television vertical sweep applications. The designer of the famous Williamson amplifier, one of the first true high-fidelity designs, suggested use of the 6SN7 since it was similar to the British triodes that he used in his circuit. In most late-1950s applications it was replaced by the 12AU7, then by transistors in the 1960s.

6SN7s are still manufactured in Russia and China under the old Soviet designator 6N8S, and continue to be used in some modern tube high-fidelity equipment.

The 6CG7 is a miniature tube (RCA, 1951) that has very similar ratings. It was also made as an 8.4V 450 mA series string type as the 8CG7.

References

* [http://tubecollectors.org/ The Tube Collectors Association]
* [http://www.mif.pg.gda.pl/homepages/frank/sheets/082/6/6SN7.pdf Datasheet on the 6SN7]
* RCA Receiving Tube Manual, RC-14, Harrison NJ, 1940
* RCA receiving Tube Manual, RC-29, harrison NJ, 1973
* Sylvania Technical Manual 14th edition (reprint), 2000
* GE Techni-Talk, Volume 6 number 5, October-November 1954
* [http://www.mif.pg.gda.pl/homepages/frank/sheets/093/6/6CG7.pdf Datasheet on the 6CG7]