KT66 is an ever popular beam tetrode tube. Very similar to the 6L6, 5881 etc... they are in many cases interchangeable as they share the 7AC pinout. As always there are differences, so always check before subbing out one valve for another.
KT66 Valves now in stock, Melbourne, Australia - The Valve Store.
Current production Russian Tung Sol KT66 tetrode tube.
GENALEX GOLD LION - Made in Russia, current production, Saratov. KT66 power tetrode.