EL34 vs 6CA7 vs KT77 ... has anyone ever compared the three?

[Dr. Tweedbucket]

I had an old Traynor YBA1A one time that had some big fat Phillips 6CA7 power tubes in it. I always meant to swap them out with some JJ EL34s and compare the two, but never got around to it.

Has anybody A-B'd an EL34 against a 6CA7 or KT77? I wonder how they compare with each other?

[eugenedunn]

Wow.....serendipity..... I just asked the same flippin' question on the TDPRI! I'll be interested in seeing responses......

I just had a vintage 1966 amp reworked recently and am looking to experiment around...... currently running vintage EL34's

Thanks everyone!

[eugenedunn]

Hi Everyone,

I recently had a cool amp undergo a big overhaul and component upgrade. It was a 1966 Kalamazoo Bass 50 amp. Details in this thread:

http://www.tdpri.com/forum/amp-centr...-tube-amp.html

The result was a really powerful amp with tons of clean headroom. It's EL34 powered, with a 6EU7 preamp, solid state rectification and simple Volume, Treble, Bass controls.

Right now I'm running some vintage National Electronics EL34's (made in East Germany) They look like dimple topped Siemens or something like that. Anyway a nice punchy clean with more midrangey aggressive character.

I feel like I want to experiment with some true 6CA7's (beam tetrodes) like the new ones from Electroharmonix (around 40 bucks) or some KT77s (kinkless tetrodes) from Gold Lion (around 78 bucks)

Anybody got any observations of using these tubes?

[Roe]

the 6ca7 sound a little more like a 6l6gc than an el34, also its more rugged. in some amps the 6ca7s sound great, esp. with a higher Z (e.g. 5k8)

[solitaire]

In theory (which adapts to practise quite easily) the fatter the bottle, the bigger the sound - and the harder vacuum the stronger the valve.

An EL34 is a true pentode and has a rather narrow bottle and soft vacuum, hence it's rather middy and has a relatively smooth and early breakup. At breakup a spongy swirling effect can appear. It's middy but compresses so that it's never really hard on the ear - or shouldn't be. E.g. JJ's and Sovtek's versions can have a bit of an edge to them.

The KT77 is a tetrode and therefore has a few tonal properties in common with the KT66, though in the EL34 realm. Being that it's slightly broader and firmer and has more clean headroom.

The 6CA7 is more of a 6L6 designed to fit an EL34 amp directly as it has the very same pinout and currentdraw of an EL34. You could almost see it as the straight bottle 6550's baby brother, with an evil crunch when it breaks up. As said it's very rugged and has a hard vacuum.

Worth adding to this trio are the JJ E34L and TungSol EL34B. The JJ has the output of a 6L6GC and some of its characteristics, with a broader tone and harder breakup. The TS EL34B is a new design where the plate impedance is tweaked to resemble that of a 6L6, which gives it a tad more highs and slightly fuller tone than most EL34s. Both of these are however true pentodes, from what I know.

[Dr. Tweedbucket]

Originally Posted by solitaire

In theory (which adapts to practise quite easily) the fatter the bottle, the bigger the sound - and the harder vacuum the stronger the valve.

An EL34 is a true pentode and has a rather narrow bottle and soft vacuum, hence it's rather middy and has a relatively smooth and early breakup. At breakup a spongy swirling effect can appear. It's middy but compresses so that it's never really hard on the ear - or shouldn't be. E.g. JJ's and Sovtek's versions can have a bit of an edge to them.

The KT77 is a tetrode and therefore has a few tonal properties in common with the KT66, though in the EL34 realm. Being that it's slightly broader and firmer and has more clean headroom.

The 6CA7 is more of a 6L6 designed to fit an EL34 amp directly as it has the very same pinout and currentdraw of an EL34. You could almost see it as the straight bottle 6550's baby brother, with an evil crunch when it breaks up. As said it's very rugged and has a hard vacuum.

Worth adding to this trio are the JJ E34L and TungSol EL34B. The JJ has the output of a 6L6GC and some of its characteristics, with a broader tone and harder breakup. The TS EL34B is a new design where the plate impedance is tweaked to resemble that of a 6L6, which gives it a tad more highs and slightly fuller tone than most EL34s. Both of these are however true pentodes, from what I know.

Thanks, that description is good and defines things a bit more.

[klippbuzz]

I found a good review on thetubestore.com site. After reading this thread I'm now considering 6CA7s for one of my vintage amps. Hope the below helps you out.

http://thetubestore.com/el34review.html

[Dr. Tweedbucket]

Originally Posted by tom.plasko

I found a good review on thetubestore.com site. After reading this thread I'm now considering 6CA7s for one of my vintage amps. Hope the below helps you out.

http://thetubestore.com/el34review.html

That was good, thanks!

[gtTelejoe]

I've tried all three and like the 6CA7EH's the most. I play blues, rock and hardrock. By the way these saturate no problem and pack a wallop in my Marshall.

Articulate, phat and make my greenbacks rip at the seams. They sound phenomenal with my NOS preamp section. Dynamics galore.

[jeff h]

I run 6CA7's in a Chicago Blues Box Humbolt head and get Fender cleans with Marshall roar.

[Roe]

I did not find that review credible. all those new tubes being as harmonically rich as the RTFs/Siemens -
If that only was the case, unfortunately most of them don't even come close. not in a marshall type ot, not in a tw, komet etc etc

[gtTelejoe]

Originally Posted by Roe

I did not find that review credible. all those new tubes being as harmonically rich as the RTFs/Siemens -
If that only was the case, unfortunately most of them don't even come close. not in a marshall type ot, not in a tw, komet etc etc

You know how the hyperbole can be sometimes...

That being said I have some RFT/Seimens EL34's and I like the 6CA7EH's more.

[blast]

I have a traynor ygl3a. It came stock with the Electro harmonix EL34's which I thought were just 'ehhhhh'. I have not tried EH's 6CA7... I would like to try the JJ KT77 and TungSol EL34b, to see if they live up to the hype. Anyway as it stands i've got 10 of these old japanese 6ca7 tubes laying around and they sound the best in the traynor... id love to know what brand they were, seem to be mullard copies.... i could stand to buy these in bulk.

an interesting note, the gold lions i've had two DOA's out of the last few sets i've ordered... kinda miserable when your paying 65 bucks a tube, so i'm not taking the chance anymore.. despite they do sound nice.

[Roe]

well el34s and 6ca7s are quite different. I like them for different applications. I use sylvanias in my comet 60 clone and RTFs in my tw express clone

[gtTelejoe]

Originally Posted by Roe

well el34s and 6ca7s are quite different. I like them for different applications. I use sylvanias in my comet 60 clone and RTFs in my tw express clone

Yeah I haven't tried the NOS 6CA7's yet and I do hear the same of what you stated about them being different than the CP versions.

I was pleasantly surprised by the 6CA7EH's. I like these better than the KT-77s as well. I have a whole drawer full of power tubes- Winged=c='s, BSTR's, Tung Sols, 34L's, RFT's, KT-77's, Mullard RI's, Svetlanas(yuk!)...

Out of all of these I prefer the 6CA7's, then the RFT's/Mullard RI's and then the Winged=C='s tone-wise.