EL34 vs. 6L6GC vs. 7591 ? Truth - Who's Best !

Gary Mattis

Active Member
I have been doing a lot of research lately on These 3 Output tubes and other than their heater currents and the typical applications there is not any real way of comparison other than amp designs and peoples opinions. I know that all 3 tubes have their own sounds, 6L6 bright, 7591 detailed, EL 34 seems to have a little bit of both with it's own smooth voice or tone. 7591 tube data is very limited and as far as I can tell 16.5 is the gain factor - if what I read was correct ? . Heater current is certainly something to consider when going from 7591 to EL 34 , but not so much on 6L6. But if the PT can handle it for say 4/hours without meltdown it is not that big of a deal unless you do not ever turn your amp off. Max PT ma. specs are not that easy to find. From my research most pre amps can easily handle the change from 7591 to 6L6 or EL 34 tubes. This seems to be over exaggerated as something that you should never do ! . I understand why they say it , they think the low heater current and max gain 5791 tube specs are everything, that is their opinion , not that I really agree with it , but I can respect it as educated also ! . The fact is 7591 tubes were given up on by most tube amp builders for some reason ? . EL 34 and 6L6 tubes are still used in just about everything with 40 watts and up ! . Which of the 3 tubes is actually the best tube ? To me The EL 34 Mullard is the best sounding tube ever made , I know that is just my personal taste and my opinion ! But I do not go directly to 6L6 or 5791 after EL 34 , Vintage Mullard, RFT, Amperex, Telefunken and Vintage Tesla. I go to 6V6 next as a little EL 34 tube. 20 to 30 watts 6V6 is my choice, Small Class A at 5 to 10 watts up to say 15 watts two EL 84 tubes I like. At 40 watts I like 6L6 tubes. At 50,75,100-130 watts I like EL 34 tubes the best. The 7591 tube has never really been on my list of favorite tubes. The Vintage Telefunken tubes though very detailed lack color or tone sometimes and can be very sterile sounding and even noisy in Phase inverters and in certain amplifiers . I have noticed Mullard 12AU7 and 6X4 have way too much bass in some amplifiers. One person can love a tube in their amp and another person can hate the exact same tube in their amplifier. I do not want to go by tube brands or amplifier companies but by overall ability and design of which tube has the best overall proven design !. Sense each tube requires fine tuning and design change it is important to know which tube is actually the best and why the 7591 was abandoned by most amp builders and tube makers !
 
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Not sure you can get any kind of intelligent answer. That is, while certain families of tubes may have a characteristic some prefer.
The same quad of whatever (you pick) in 5 differents amps (different driver stages, OPTs, can have different sounds.
It's possible to find preferences within a given group.
One last point, all E34s, 7591s, 6L6s aren't created equal so even within a single type you may have preferences. My 2c
(Worth exactly that:biggrin:)
 
well, they're different. Best is very subjective and depends on the circuit. They have different loading and drive requirements too, so they don't just drop in for each other in an amp to allow for direct comparisons either.
 
A comprehensive response to this would take 5-10 letter sized pages of text.

The "sound" you hear comes from the speakers, not the tube. When you put different tires on your car the road sound changes because of the tread design and may sound louder on your car but if someone puts those on their car the sound may be quieter.

Tell us why a tube would sound "bright." Tell us something about the range of frequencies that a 6L6 tube can pass to the output transformers and speakers as opposed to other tubes you mention. Does it make any sense?
Good answer about the OT's and speakers with each tube , each one influences the sound in a major way. On plate voltage and current is the EL 34 superior to the other two tubes or to most audio tubes that are being mass produced ? Or is that not really that important sense a lot of amp makers exceed values all the time anyway ? There is not a big change in the sound to me between output tubes, usually it is just certain things some tubes are better at than others. That is why I was trying to find out which tube is best overall . Seems like there is an answer, but No real answers to my question , I guess because of peoples choices. It varies according to our taste and the design in the end. If you get a good design, good tubes, good speakers and a good pre amp and good source it all comes together in the end results, tubes are just an important part of it like a master link in a chain. I like the fact we can change tubes to change or re arrange the sound that our amps make. I guess looking at The Bigger Picture has to be the correct answer.
 
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7591s were made for integrated amps so they could a more compact look. Short and stubby they fit into small spaces. With the advent of transistors tubes were considered inferior. 7591s showed up too late in the game. I've changed many to 6L6s, no problem. I've had people tell NO, it won't work. I want to try Tungsol reissue stubby 6L6s which mite by the same as their 7591s. 6L6s are the most common power tube, for a good reason. Some of the new 6L6s are impressive, many choices.
 
Different tube types were designed with different operational and performance goals in mind. That point is everything. Trying to establish which one is best based on a given perception of sound produced in a given circuit is an exercise without end, as the exercise is entirely subjective. It is the circuit that determines the outcome of the sound produced. Changing to different tube types will likely produce a different sound from a given circuit -- but the change in sound is not directly due to the qualities of the different tubes. It is because the qualities of the different tubes have now changed the way the circuit operates and performs.

Dave
 
Different tube types were designed with different operational and performance goals in mind. That point is everything. Trying to establish which one is best based on a given perception of sound produced in a given circuit is an exercise without end, as the exercise is entirely subjective. It is the circuit that determines the outcome of the sound produced. Changing to different tube types will likely produce a different sound from a given circuit -- but the change in sound is not directly due to the qualities of the different tubes. It is because the qualities of the different tubes have now changed the way the circuit operates and performs.

Dave

Thanks Dave for your comment. I have backed away from this current "exercise" because of the subjectivity of the assumptions. I am more into verifiable facts and not opinions unverified. But that being said, it is wonderful that each of us can have said opinions and be totally free to do with our equipment, whatever we want.

I don't have a "favorite" tube. But I guess if I had a favorite tube would actually be the tube that the circuit was designed for. Any notion of tube Number "X" sounding brighter or fuller or whatever is exactly what you described; the design of the circuit and more importantly, speakers.

And like above, just my 2¢ for what it's worth (And I don't know of any penny candy stores anywhere now! ;) )
 
Different tube types were designed with different operational and performance goals in mind. That point is everything. Trying to establish which one is best based on a given perception of sound produced in a given circuit is an exercise without end, as the exercise is entirely subjective. It is the circuit that determines the outcome of the sound produced. Changing to different tube types will likely produce a different sound from a given circuit -- but the change in sound is not directly due to the qualities of the different tubes. It is because the qualities of the different tubes have now changed the way the circuit operates and performs. Dave

This should be on a banner at the top of the AK tube home page.
 
7591 was one of the last output tubes ever designed which means it incorporated the greatest amount of prior knowledge & experience of tube design & engineering at that point. In the right equipment, it's difficult to criticize the sonic capabilities to be had from quality set of 7591.
 
It entirely depends on the operating point and the circuit.

I've made 6V6s and 6L6s sound a LOT like KT88s and 6550s.

I've made EL84s sound like 7591s.

With the right loading, bias, circuit design, feedback implementation and transformer selection, great amps can be made with almost any good tube type...

Regards,
Gordon.
 
It's obviously circuit dependent and how it interacts with a given speaker. In my set up the 6L6 sounds too lean in the upper bass and lower mids. Like a bad SS amp. The EL34 sounds much better. However finding the right driver tube is more important and should be settled first. imo.
 
7591 was one of the last output tubes ever designed which means it incorporated the greatest amount of prior knowledge & experience of tube design & engineering at that point. In the right equipment, it's difficult to criticize the sonic capabilities to be had from quality set of 7591.

Hear, hear.

The engineers knew what they were doing. That's what they were trained for and had experience in. I certainly am not an engineer and have no intention to second guess them. Westinghouse was the creator of the original 7591 and very few American manufactures made them. Most were re-branded Sylvania or Westinghouse manufacture. However Hitachi and Toshiba made them in Japan.

I guess the only comparison would be the 7868 which appears to be very similar to the 7591 albeit in a Novar envelope.
 
The 8417 would also fall broadly into that category, but it was a higher power tube. Similar goals with being easy to drive, its sort of like a biggie-size 7591 Same sort of issues too, late release, not very high production, except that nobody is making one at all now.
 
The 8417 would also fall broadly into that category, but it was a higher power tube. Similar goals with being easy to drive, its sort of like a biggie-size 7591 Same sort of issues too, late release, not very high production, except that nobody is making one at all now.

Even GE never got the 8417 right, I wonder how the modern tube makers would do. I know I'd pick some up if it did come back on the market.
 
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