its use. Generally speaking, 6V6 tubes are sturdy and can be operated beyond their published specifications (the Soviet made 6P6S, and early Chinese 6V6 versions were not as permissive of exceeding design limits, although current production has improved). Because of this, the 6V6 soon proved itself to be suitable for use in consumer-market musical instrument amplifiers, particularly combo-style guitar amps such as the Gibson GA-40, and the Fender Amplifiers; Champ, Princeton, and Deluxe, some of which drive their 6V6s well in excess of the datasheet specified maximum rating. This ongoing demand encourages Chinese, Slovakian and Russian tube factories not only to keep the 6V6 in production to this day, but to further develop the supply. The 6V6 Family and equivalents 6V6G – Glass "Shouldered Tube" ST envelope. 6V6GX – Glass "Shouldered Tube" ST envelope, Ceramic Base. 6V6 – Metal jacketed envelope. The metal envelope of 6V6 is connected to pin 1 of the base, and was normally used as a ground. Pin 1 of the other members of the 6V6 family of tubes are usually not internally connected, although some may have the gray RF shield connected. 6V6GT – smaller "Glass Tube" T-9 envelope. 6V6GTA – with a controlled warm-up period. 6V6GTY – a GT with a low loss micanol brown base. 6V6GTX = HY6V6GTX – a GT "Bantam" selected for high gain, with a ceramic base, 15W plate dissipation rating, produced for a limited period around 1941 by Hytron. 5871 – Ruggedized 6V6GT for operation under severe vibrations found in aircraft and similar applications. Radio Valve Co. of Canada Ltd., 1954 : RMA #859A. 5992 – Premium, ruggedized 6V6GT with heater current raised to 600mA. Bendix and GE known manufacturers. 7408 – 6V6GT with additional zero-bias characteristics. 6V6S – A modern production, large plated tube, heater current 500mA, with a higher plate and screen voltage rating. Made by JJ Electronic. 6V6GT(A)(B)-STR – Modern production valve, STR signifying "Special Test Requirement." Claiming to be heavy duty, suitable for high plate voltage. Military specification 6V6 tubes and their equivalents American military services contracted tubes from many sources through the U.S. War Department. They used a Joint Army-Navy Nomenclature System (AN System. JAN) Most of these tubes bear the JAN marking as well as a VT number (VT = vacuum tube). VT-107 – Metal 6V6. 6V6Y – Metal, with a low loss micanol brown base. VT-107A – 6V6GT. VT-107B – 6V6G. British