6CA7 instead of EL34

Bourney

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stoke on trent
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Could 6CA7s be used in place of EL34s in any amp or could some amps not like them? Specifically a unison research S6.

Ta

 
M

MallyMad

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Check with the manufacturer but they usually are a drop in replacement. Mind the biasing though.

 

old_school

Wammer
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Dec 8, 2011
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Jay
They are identical. 6CA7 is the US naming convention for EL34. Regardless, if you have manual bias you'd need to check it anyway if you change valves.

 

i_should_coco

Wammer
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Not quite true, the original 6CA7 is a beam tetrode, designed to get around Philips' pentode patent while the EL34 is a true pentode. Electrically, they're interchangeable, however.

Wouldn't surprise me if some modern production variants are the same thing with different labels, however.

 

rabski

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Original S6 was auto bias, new version is manual, but done externally with panel meters fitted. If there aren't meters and bias adjustment controls, it's the auto version. Advisable therefore, however, to get as close matched tubes as possible.

 

meninblack

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My Air Tight is labelled for 6CA7, but it's always had EL34s in it. Actually it now has E34L, whatever difference that makes.

(I just stick any old tubes in, then Pete swears at it for a bit while biasing it because the twiddle pot is hidden behind the high-tension electrocuter, or some such. :dunno: )

 

i_should_coco

Wammer
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My Air Tight is labelled for 6AC7, but it's always had EL34s in it. Actually it now has E34L, whatever difference that makes.(I just stick any old tubes in, then Pete swears at for a bit while biasing it because the twiddle pot is hidden behind the high-tension electrocuter, or some such. :dunno: )
Hah! Stupid thing is designed to try to kill you while biasing. :x

As noted, EL34 and 6CA7, although nominally different things should be the same. No changes over and above what you'd do for another brand of EL34 should be needed (just re-biasing in the case of fixed-bias).

 

Bourney

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Think I'm safe then Pete? Mine is the older S6 - auto bias one.

im told the 6CA7 has less fat on its arse and is bit cleaner sounding than the rich and meaty EL34 sound?

 

i_should_coco

Wammer
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It will be fine, just get matched pairs per channel.

As for how tubes sound, I think my opinion is well known in that I don't believe tubes have a sound, except in the context of an amplifier.

 

lordmortlock

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Drop RSand a Pm Steve if you want another opinion. He has the Quintet now and both your original '34s and the EH 6ca7s I was playing with.

 

myrman

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I put a quad set of 6CA7s in my Art Quintet recently. A definite improvement over the EL34s.

 
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MallyMad

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Yip - I swapped out Svetlana EL34s for Black Treasure 6CA7s and the sound is different. My setup sounds superb just now but I wouldn't say the BTs are better or worse - just different. Both sets of tubes sound fantastic and I've a quad of Siemens to try soon as well. I'm also keen on swapping out the 6N3s/2C51s - well cheap and definite improvements here and there.

 

RSand

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I put a quad set of 6CA7s in my Art Quintet recently. A definite improvement over the EL34s.
Funny, I prefer the EL34's in my quintet over the 6CA7's, this says a lot for both personal tastes and synergy with the rest of the system.

I found them lacking in weight and a bit aggressive sounding however after a phono stage change I'll have to try them again and see if this is still the case. When I first brought the quintet home I installed the 6CA7's and after an evening of music my wife said "that sounds awful I preferred your old amp" - I agreed! After popping the winged c's in it sounded wonderful.

I'll try them again this week. There may well be a matched quad of EH 6CA7's with around 30 hours on them in the classifieds ;)

 

old_school

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Not quite true, the original 6CA7 is a beam tetrode, designed to get around Philips' pentode patent while the EL34 is a true pentode. Electrically, they're interchangeable, however. Wouldn't surprise me if some modern production variants are the same thing with different labels, however.
Good point. I probably should have said "functionally identical." Lots of Phillips and Mullard EL34s wound up in the US with Fisher, Dynaco and Realistic labels and 6CA7 numbering on them. I once had a pair of Mullard xf2 branded Realistic (Radio Shack's house brand) and labelled 6CA7.

 

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