EL34 vs. KT77?

[FlyingSkull]

Hello, wondering if anyone can shed some light on this for me?

Wondering if there is any appreciable difference between El34 and KT77 tubes?

The reason I am mixed up here is that in some documentation I see, the terms are used interchangeably, and other times referred to in a manner that makes them appear quite different sonically etc.

And if they are different musically, do you have to rebias your amp to switch ex EL34 to KT77?

Thanks for you help, I eagerly await the rapid clicking of your helpful keyboard keys!

[Cygnus X1]

Same tube, different nomenclature.
One is British naming, the other US.

Yes, many different brands/sounds.
Which amp do you have, and what sort of sound are you pursuing?

Another note-anytime you change power tubes, you need to rebias unless it is a cathode (self biasing) amp...which is rare.

[DonP]

Same tube, different nomenclature.
One is British naming, the other US.

Yes, many different brands/sounds.
Which amp do you have, and what sort of sound are you pursuing?

Another note-anytime you change power tubes, you need to rebias unless it is a cathode (self biasing) amp...which is rare.

Are you serious?

Totally different tube. The EL34 is a true Pentode, the KT77 is a Kinkless Tetrode.

Both are British tubes.

6CA7 is the US equivilent of the EL34.

Self biasing is common for lower wattage < 30 watt amps, not common for higher wattage.

Highly likely that you would need to re-bias switching from EL34 to KT77.

[toejam]

The KT77 is a direct replacement for the EL34; though, their impedence is a little higher and closer to a 6L6, so you might need to rebias, but some people say you don't have to. The KT77s have more low end and are a little tighter sounding, less midrange honk, too.
http://www.eurotubes.com/euro-e.htm

[DonP]

The KT77 is a direct replacement for the EL34

Yes, but the design is different and that would prevent the two from sounding similar.

[FlyingSkull]

Thanks guys that is some good info, I understood they both fit in the same sockets but was unsure of any actual technical differences, but I have more to go on now, thanks.

[Spivonious]

6CA7 = EL34? I always thought that 5881 = EL34.

And Cyg - major disappointment. You build amps, don't you?

[toejam]

6CA7 = EL34? I always thought that 5881 = EL34.

6CA7 is an EL34 equivalent.

5881 is the equivalent of a 6L6 or KT66.

[DonP]

6CA7 is an EL34 equivalent.

5881 is the equivalent of a 6L6 or KT66.

+1 for Toejam

The 6L6 is a Beam Power Pentode, the US equivelent of Europe's Kinkless Tetrodes.

6550 is also a beam power, ~= KT88.

[Cygnus X1]

6CA7 = EL34? I always thought that 5881 = EL34.

And Cyg - major disappointment. You build amps, don't you?

Yes, cathode biased.
I had my beer goggles on, thank you all for clearing it up for me.

I'll stand by my biasing statement tho.

[DonP]

Yes, cathode biased.
I had my beer goggles on, thank you all for clearing it up for me.

I'll stand by my biasing statement tho.

I'll give props to Cyg, he is building amps. Wish I had the time to get off my butt and build some more. Too much work, kids, and on the road just sucking down all of my time.

[nor]

kt-77's were marketed as a premium el-34 and priced accordingly. Even now the nos 77's can fetch over 1k each. The tone is (i've heard) a cross between el-34 and 6l6. As far as biasing - depends on the amp/situation - but you most likely will need to bias to get the most out of the tubes you switch to.

[Eric_kv2]

I tried KT-77's when I had an Engl SE and Framus Cobra. It seemed to clean the amps up a little (more articulate) and take away some of that midrange honk that EL-34's are known for. You'll either like them or hate them. I've also heard them in splawn quickrods and they sound awesome in that amp.