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el34 vs 6ca7

onemug

onemug

Super Member
In an amp that can use either of those, can someone describe, in general, the differences in sound between them if used in the same amp.

I know that even different brands of the same tube can sound different so that's why I mentioned "in general".
 
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The 6CA7 fat bottle uses beam tetrode construction. Therefore, they will tend to sound similar to a 6550. Not as warm or romantic as a Mullard XF2 EL34 but with great dynamics and extension.

My favorite of the 6CA7 Fat Bottles are the Sylvanias. Had a quad of them a few years ago and sounded excellent on my Marantz 8B.

Guitar folks love 'em for their break up characteristics and "crunch". Eddie Van Halen supposedly has hoarded most of them for his personal stash...
 

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crooner said:
The 6CA7 fat bottle was derived from the 6L6 with similar beam tetrode construction. Therefore, they will tend to sound similar to a 6L6. Not as warm or romantic as a Mullard XF2 EL34 but with great dynamics and extension.
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I've thought of it as a smaller 6550 as the structure is similar, more so than that of a 6L6 tho all are sheet beam kinkless tetrodes.

Sent from my SM-N900V using Tapatalk
 
Pio1980 said:
I've thought of it as a smaller 6550 as the structure is similar, more so than that of a 6L6 tho all are sheet beam kinkless tetrodes.

Sent from my SM-N900V using Tapatalk
Click to expand...

True, they were designed using 6550 tooling. Corrected my original post to reflect this.
 
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I always thought an EL34 and a 6CA7 were interchangeable....kind of like an EL84 and a 6BQ5. Is that not true?
 
StuartB said:
I always thought an EL34 and a 6CA7 were interchangeable....kind of like an EL84 and a 6BQ5. Is that not true?
Click to expand...

They are, but the internal construction method is different. The 6CA7 "Fat Bottle" uses a virtual suppressor grid in its beam tetrode construction. The EL34 is a true pentode.

Electrically they behave the same, with similar characteristics.

In the case of the 6BQ5, it's just the American designation of the EL84, no difference in construction.
 
The EL34 was a Mullard design, and the 6CA7 was who, Sylvania? I believe it was developed to compete with the EL34, but they based the design around existing beam tetrodes rather than duplicate the pentode design of the Mullard tube.
 
I have seen RCA 6BQ5 tubes in both the pentode and tetrode this was not a rebrand, it had the flattened round RCA plates. I believe the EL84 was designed as a pentode (In Europe) and the 6BQ5 was based on a miniaturized 6V6GT tube (America). They are also interchangeable.
 
^^^Thanks above^^^

btw and in case anyone is interested, the amp I am trying out is a Scott 290.

So far...It does sound like the 6ca7 is similar to the 6550 family. I say so far because I "just" found out the amp has a brand new power supply and the caps are forming. I actually did not care for the sound that much at first fire up but within 2 to 3 hours it started sounding like I would expect?/hope.

I'll be putting more hours on it and see how it goes.
 
I've always preferred the Sylvania 6CA7 over any EL34.Personally,I found them to be a tighter,cleaner sounding alternative to the EL34. They also seemed to be much more reliable,stable,and less prone to microphonics and rattles. Used to use them in my Dyna 70's,and man did they ever sound good in Hiwatt and Sound City guitar amps! Kinda regret having installed so many of them in amps used by guys whose idea of tone was every knob on ''11'':D

What I wouldn't give for a couple of dozen of these now:sigh:

For many years I used a pair of rack-mount Hiwatt Tube-State 200R power amps(first in my bass rig,later in my home stereo),which run 6x EL34's at 650+ volts on the plates.
Only the Sylvania 6CA7's were ever able to run reliably in these monsters.Nuff said....Here's a link to the only pic I could find on the interweb:

http://www.guitarscanada.com/showth...-amp-good-platform-for-high-gain-preamp/page2
 
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I really like them in my ST-70 also. If your going to try them, buy from The Tube Store, Tube Depot,Tubes and More, or Jim McShane. Tubes and More puts a label.on the base of the tube showing the test results. Also pay the extra buck or so to get matched sets.
 
Lavane said:
I really like them in my ST-70 also. If your going to try them, buy from The Tube Store, Tube Depot,Tubes and More, or Jim McShane. Tubes and More puts a label.on the base of the tube showing the test results. Also pay the extra buck or so to get matched sets.
Click to expand...


I bought a matched pair of Russian 6N2's from these guys and each had the handwritten specs. The prices here a great too:

https://www.vivatubes.com/new-matched-pair-2-electro-harmonix-6ca7eh-fat-bottle-vacuum-tubes/
 
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