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Tube Database (7,341 tube types · 1,270 archive entries)

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KT77

Brand
Genalex

Round Tip

Base
Brown
Bottle Height
Tall Bottle
Bottle Shape
Skinny Bottle
Country
England
Glass Color
Clear Glass
Mica
Double
Notes
"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 (link: http://vintageamps.com/plexiboard/viewtopic.php?f=13&t=26997 text: Vintage Amps Forum), "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 (link: http://vintageamps.com/plexiboard/viewtopic.php?f=13&t=26997 text: Vintage Amps Forum)
Archive ID
84potj3d
Plate Color
Matte Gray
Plate Look
Smooth
Tip Shape
Round Tip

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    U77, GZ34, 5AR4

    Brand

KT88

Maker
M.O.
Brand
Genalex

B759

Brand
Genalex, Gold Lion

B749

Brand
Genalex, Gold Lion

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Maker
M.O.
Brand
Genalex

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Maker
M-O Valve Co. Ltd
Brand
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Brand
Genalex

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Maker
M-O Valve Co. Ltd
Brand
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Brand
Genalex
Genalex

Equivalent and related tube numbers

Commonly cross-referenced designations for KT77. Compatibility is not guaranteed. Before substituting, verify socket and pinout, heater voltage and current, bias requirements, and maximum ratings against the relevant manufacturers’ datasheets.

  • 6CA7
  • EL34

More KT77 type tubes

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KT77

Maker
National
Brand
RFT
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    Brand
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    Brand
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