Although the
RCA 6L6 of 1936 (the result of a license agreement between RCA and
EMI) was the first successful beam power tube on the market, the KT66 of 1937 became almost equally famous, at least in Europe. Because the beam tetrode design eliminated the
tetrode kink in the lower parts of the tetrode's voltage-current characteristic curves, M-OV marketed this tube family as the "KT" series, standing for
kinkless tetrode. The KT66 was one of the "International series" introduced in 1937. This series utilized the "American Octal" base and had characteristics equivalent to tubes by U.S. manufacturers. in Saratov, Russia (
Genalex Gold Lion brand), JJ Electronic in Slovakia, and by
Hengyang Electronics at former Guiguang factory in Foshan city, southern China. Some modern Russian manufacture Sovtek KT66 tubes are actually 6L6GC tubes in a KT66 style bottle. While these tubes have the same pinout and minimum tolerances required of a KT66 tube, they do not have the performance characteristics of a true kinkless tetrode KT66 tube. By contrast the very latest Russian manufactured tubes (2012) not only carry the same internal electrode structure as the original KT66 (they now look the same) they also have the same rugged electrical characteristics and can withstand a high voltage on grid 2 comparable to the anode voltage rating, allowing greater power output afforded by higher voltage capability when run in ultralinear connection. ==See also==