Brand on Tube Genalex

Country England
Bottle Height Tall Bottle
Tip Shape Round Tip
Bottle Shape Skinny Bottle
Glass Color Clear Glass
Mica Double
Plate Look Smooth
Plate Color Matte Gray
Base Brown

"GEC lists real KT77 as of the '70s as absolute max ratings of 850V plate/650V screens/32W max plate dissipation- they're ultra tough. Design center ratings are 800/600/25. Original EL34s were rated 800V plates (!), but the real weak link since they're pentodes is the screen grid, which was actually rated 425V max from the beginning, even though we all violate that everyday, right? No question real KT77s will take more for longer than real EL34; the KT77 is actually a beam tube, like pretty much all GEC power tubes of note, not original-style pentode. Competitor to EL34! I haven't experienced them very extensively, so I'd be interested to hear your sonic/feel impressions. Mine are that most would call them a little harder sounding than Euro EL34s, stay a little or maybe a lot edgier when pushed, but they still distort and everything. I know some folks really like them, and they're desirable because of that, their durability, and they're relatively scarce I think. Appeared in late '50s, maybe by '58; through at least early '60s they're flat topped like double-D Amperex EL34, w/small brown bases and cool red Genalex decals- these are the most expensive- sometime by '70s they're still narrow and tubular but dome-topped, rounded at the end. The latter were stock in some Marshalls in the '70s. A lot of them apparently were Gold Lion branded, even through the '70s. They might need a little more bias than typical EL34, that's my memory, but in general they were intended to be drop-in replacement. Filament current is 1.4A, BTW, about the same as EL34 if not slightly less. As stated, GEC said a pair in AB1 was good for over 70W continuous."

From a post from Jeff W. on Vintage Amps Forum

Genalex KT77
Genalex KT77

Lets discuss this tube