6V6 is the designator for a vacuum tube introduced by Radio Corporation of America RCA United States in late 1937. RCA, formerly an initialism for the Radio Corporation of America, is now a trademark used by two companies for products descended from that common ancestor: Thomson SA, which manufactures consumer electronics like RCA-branded televisions, DVD players, video cassette recorders, direct broadcast satellite decoders, camcorders, audio equipment, telephones, and related... 1937 was a common year starting on Friday (link will take you to calendar). ...

6V6 is a beam-power pentode, similar to its predecessor the 6L6. While the 6L6 was an excellent tube, it was not really suitable for use in home consumer electronic devices because its output, especially in a push-pull pair, was so high. With the introduction of the lower-powered 6V6, which required only half the heater power of the 6L6, the beam-power pentode because a usable technology for the home, and began to see common use as the audio output stage of radios and other electronic home entertainment devices where standard power pentodes such as the 6F6 had previously held sway. The 6V6 required less heater power and provided less distortion than the 6F6, while still offering higher output in both single-ended and push-pull configurations. In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal. ... Pair of 6L6GC tubes; (l) General Electric version from 1960s, (r) current manufacture from Svetlana Electron Devices, Russia 6L6 is the designator for a vacuum tube introduced by Radio Corporation of America RCA United States in July 1936. ...

The 6V6 was introduced in both metal and shouldered glass tubes. RCA was promoting the superiority of its metal tube designs in the second half of the 1930s, and this tube, having been introduced during that period, was produced in large quantities in this format. Other tube manufacturers also produced the 6V6 in glass tubes, which were commonly found in radios not made by RCA. By 1940 the 6V6 was mostly being produced in a smaller "GT" glass envelope, and later the 6V6GTA was introduced which had a controlled warm-up period. Also similar is 6AQ5, which has similar specifications but in a miniature glass shell, and the 7408. // Events and trends The 1930s were spent struggling for a solution to the global depression. ... 1940 was a leap year starting on Monday (link will take you to calendar). ...

These tubes are sturdy and can be run beyond their published specifications. Because of this, the 6V6 became very popular for use in instrument_amplifiers. This market allows Slovak and Russian tube factories to keep the 6V6 in production to this day. This page is about amplifiers for musical instruments. ...

References:

* Stokes, John, 70 YEARS OF RADIO TUBES AND VALVES, Vestal Press, NY, 1982