EL34 or 6L6

AP515

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I started on Fender amps and loved the cleans. So 6L6's were my go to valves. (I'm not English, I know, they are tubes. Just wanted to tweak y'all). Then I got the SE50 with EL34's and I was hooked. So now I like both sets. Each for what they do well.
 

Egads

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I love how well designed amps can take the character of a tube and bring out the most of it. Likewise, an amp can be built with EL34s and sound like a BF fender, or 6L6s and bark like a Marshall.

I have a few amps that can utilize almost any octal tube. It changes the feel, headroom, and tone (to a lesser extent than the two previous items). The amp still sounds like what it is, but just a different variation. The changes in feel and headroom are WAY more drastic.

BTW, in all three amps, I like KT66 tubes for tone, feel, and dynamics. Big transformers help. They bring out the percussiveness and thump.
 

Em7

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Speaking of the KT66, another tube that people who like the EL34 should try is the KT77. The 2-Channel H sounds great with KT77s installed. The KT77 is a beam tetrode that is a direct replacement for the EL34. It is to U.S. 6CA7 what the KT66 is to the 6L6GC (the 6CA7 is another direct replacement for the EL34). The KT77 and the 6CA7 tubes lie in between the EL34 and the 6L6GC sonically. The Marshall used on Van Halen's debut album had 6CA7s installed. It was not uncommon for 6CA7s to be installed in Marshalls in the United States during the 70s. Most the Marshalls that Rose-Morris shipped to the United States during the 70s came with 6550s installed. They did so in order to ensure that the amps would make it through their warranty period. A 6550 is much more rugged than an EL34 with its slender envelope and soft vacuum. I am absolutely certain that Marshall installed a fuse on the B+ voltage to protect the output transformer from premature death due to an EL34 shorting out. Big bottle 6CA7s are much more robust than EL34s. They are great sounding tubes for the guitarist who wants the mids of an EL34 and the bottom-end of the 6L6GC.
 

Em7

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I had a Shiva 20 with kt88 and it had great mid presence plus lots of bottom end and a nice raspy character.

The KT88 is to the 6550 what the KT66 is to the 6L6GC and the KT77 is to the 6CA7. They are all beam tetrodes. However, KT88s and 6550s can handle voltages and plate dissipations that would kill the other tubes.
 

SilverSurf9

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Very interesting discussions here. Good points all around. Speaking of less common tubes than the 6L6/EL34, one of my favorite amps in the current stable is the Carol-Ann Tucana 3, which uses a pair of KT88s. This is the first amp I’ve owned using those tubes, and man are they nice. They can get quite loud while remaining clear and full, and if you can stand the volume (I use an Ox Box) the response is glorious when they pour on the power. I’ve currently got a set of SED Winged C tubes in, and I love the power of this amp.

I’m no expert on these tubes, but this amp, as a package, is a tone monster. I’ve read a lot on their history, but just don’t see them a lot. Anyone else using KT88s?

I see why people like KT88's but I prefer 6550 over KT88... They are almost the same tube and are interchangeable but the 6550 will crunch more. The KT88 is pure headroom. Both are great for cutting through the mix with blunt force especially if you are using a lot of pre-amp gain.

To the original poster - KT77 and 6CA7 are right in the middle of a 6L6 and EL34.
 

RickP

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I see why people like KT88's but I prefer 6550 over KT88... They are almost the same tube and are interchangeable but the 6550 will crunch more. The KT88 is pure headroom. Both are great for cutting through the mix with blunt force especially if you are using a lot of pre-amp gain.

To the original poster - KT77 and 6CA7 are right in the middle of a 6L6 and EL34.
The Carol-Ann Tucana 3 changed my mind on what I thought the KT88 was all about, or could do. Try one if you get the chance. There’s no way to just explain it.

This is a part of what took me to dumping the “I play only tube type A, B, C” opinion. It’s the package it’s built into that determines what it can do. All of the components contribute in larger or smaller amounts to the amp performance characteristics. If you prefer any particular tube because of what it does in a particular amp, by all means, enjoy that amp! Don’t let tube lore limit you too much.
 

markd21

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...If you prefer any particular tube because of what it does in a particular amp, by all means, enjoy that amp! Don’t let tube lore limit you too much.

Right on! The cleans I like are Fender Black or Silver based. I want a 6L6. I can do cleans with an EL34, it's just a different texture. Shoot, once I discovered Bad Cat I found a love for the EL84s that I never had before. The clean is very harmonically rich with the Cub circuit.

Crunch tones HAVE to be British tube based for me. I like mids and find the EL34 and el84 provide the mids I like.
 

SilverSurf9

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The Carol-Ann Tucana 3 changed my mind on what I thought the KT88 was all about, or could do. Try one if you get the chance. There’s no way to just explain it.

This is a part of what took me to dumping the “I play only tube type A, B, C” opinion. It’s the package it’s built into that determines what it can do. All of the components contribute in larger or smaller amounts to the amp performance characteristics. If you prefer any particular tube because of what it does in a particular amp, by all means, enjoy that amp! Don’t let tube lore limit you too much.

I totally hear ya... it all depends on the amp and how its wired. I dont have a particular tube that I stick with but I enjoy some more than others. What I noticed too, is how important the bias is set. I think that is what makes the peavey 5150 so good is it's cold bias which is perfect for metal and palm muting. But I dont think a marshall would sound good with a cold bias... all depends on setting.
 

ViperDoc

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To get the most out of a proper power tube comparison, you have to include running each power tube with its correctly-specified output transformer primary impedance. A 2203 with EL34 tubes will be designed with an OT that shows them a primary impedance of about 1.7 Kohms, whereas the KT66 wants to see about 4 Kohms. Usually a tube swap will just involve a rebias, but without an OT swap, you’ll never really hear what the KT66 can do. It will sound good, but not true to it’s potential. And THEN, there are the speakers, which HUGELY AFFECT TONE. And then there’s amp-voicing, gain stage and EQ placement, etc. It’s a huge puzzle, man. There are lots of people who are breaking the classical rock circuit rules with amazing results, so the best thing to do is just play a lot of amps and see what you think.
 

SilverSurf9

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To get the most out of a proper power tube comparison, you have to include running each power tube with its correctly-specified output transformer primary impedance. A 2203 with EL34 tubes will be designed with an OT that shows them a primary impedance of about 1.7 Kohms, whereas the KT66 wants to see about 4 Kohms. Usually a tube swap will just involve a rebias, but without an OT swap, you’ll never really hear what the KT66 can do. It will sound good, but not true to it’s potential. And THEN, there are the speakers, which HUGELY AFFECT TONE. And then there’s amp-voicing, gain stage and EQ placement, etc. It’s a huge puzzle, man. There are lots of people who are breaking the classical rock circuit rules with amazing results, so the best thing to do is just play a lot of amps and see what you think.

Indeed.... there is a lot of room for creativity in amp design. Sometimes I wonder what a 5150 would sound like with 6550s with a cab loaded with g12h30. Wish I had more money to spend and a bunker to krank amps to 10. Marty McFly.
 

Em7

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To get the most out of a proper power tube comparison, you have to include running each power tube with its correctly-specified output transformer primary impedance. A 2203 with EL34 tubes will be designed with an OT that shows them a primary impedance of about 1.7 Kohms, whereas the KT66 wants to see about 4 Kohms. Usually a tube swap will just involve a rebias, but without an OT swap, you’ll never really hear what the KT66 can do. It will sound good, but not true to it’s potential. And THEN, there are the speakers, which HUGELY AFFECT TONE. And then there’s amp-voicing, gain stage and EQ placement, etc.

That is not quite correct. First off, output transformers do not have fixed primary impedances. The primary impedance of an output transformer is dependent on the what is attached to the secondary winding because transformers have impedance ratios. For example, your typical 8K ohms to 8 ohms transformer has an impedance ratio of 1000 to 1 (1000:1), which means that if we attach a 16 ohm speaker to the secondary winding, the amp will see a reflected primary impedance of 16K ohms. Every output transformer has an impedance ratio, which is the primary impedance divided by the secondary impedance. Output transformers with multiple output impedances have multiple taps on the secondary winding that set the impedance ratio for the tap with respect to the primary winding. The impedance ratio is the square of the turns ratio. In the case of the 8K to 8 ohms output transformer, the impedance ratio is 1000:1 and the turns ratio is 31.62:1 (the square-root of the impedance ratio).

Secondly, if we double the number of output tubes, we halve the primary impedance requirement. The 2204 has a duet of EL34s and is designed with a reflected primary impedance of 3.4K in mind. The 2203 has a quartet of EL34s and is designed with a reflected 1.7K in mind. A duet of 6550s will operate well with a reflected primary impedance of 3.4K and a quartet of 6550s will do the same on a reflected primary of 1.7K (that is why the 6550 was the output tube of choice for Marshalls shipped to the US in the 70s). We need to keep in mind that these figures are nominal values because impedance is not a synonym for DC resistance. Impedance is an AC unit of measure and it changes with respect to frequency due to its reactive component (i.e., impedance Z = SQRT(R^2 + (Xl -Xc)^2), where SQRT = square-root function, the symbol “^” denotes raised to the power of, R = resistance in ohms, Xl = inductive reactance, and Xc = capacitive reactance). What this difference means is that the reflected primary impedance that a power tubes sees changes with respect to frequency due to the fact that a speaker’s impedance changes with respect to frequency. That is why tube amps are more sensitive to the chosen loud speaker than solid-state amps.

One last thing, if one looks at the data sheets for a power tube, one will see multiple primary impedance values, often with the same operating parameters except for primary impedance. What this means is that primary impedance should be selected for tone and desired output efficiency, that is, within constraints.
 

ViperDoc

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That is not quite correct. First off, output transformers do not have fixed primary impedances. The primary impedance of an output transformer is dependent on the what is attached to the secondary winding because transformers have impedance ratios. For example, your typical 8K ohms to 8 ohms transformer has an impedance ratio of 1000 to 1 (1000:1), which means that if we attach a 16 ohm speaker to the secondary winding, the amp will see a reflected primary impedance of 16K ohms. Every output transformer has an impedance ratio, which is the primary impedance divided by the secondary impedance. Output transformers with multiple output impedances have multiple taps on the secondary winding that set the impedance ratio for the tap with respect to the primary winding. The impedance ratio is the square of the turns ratio. In the case of the 8K to 8 ohms output transformer, the impedance ratio is 1000:1 and the turns ratio is 31.62:1 (the square-root of the impedance ratio).

Secondly, if we double the number of output tubes, we halve the primary impedance requirement. The 2204 has a duet of EL34s and is designed with a reflected primary impedance of 3.4K in mind. The 2203 has a quartet of EL34s and is designed with a reflected 1.7K in mind. A duet of 6550s will operate well with a reflected primary impedance of 3.4K and a quartet of 6550s will do the same on a reflected primary of 1.7K (that is why the 6550 was the output tube of choice for Marshalls shipped to the US in the 70s). We need to keep in mind that these figures are nominal values because impedance is not a synonym for DC resistance. Impedance is an AC unit of measure and it changes with respect to frequency due to its reactive component (i.e., impedance Z = SQRT(R^2 + (Xl -Xc)^2), where SQRT = square-root function, the symbol “^” denotes raised to the power of, R = resistance in ohms, Xl = inductive reactance, and Xc = capacitive reactance). What this difference means is that the reflected primary impedance that a power tubes sees changes with respect to frequency due to the fact that a speaker’s impedance changes with respect to frequency. That is why tube amps are more sensitive to the chosen loud speaker than solid-state amps.

One last thing, if one looks at the data sheets for a power tube, one will see multiple primary impedance values, often with the same operating parameters except for primary impedance. What this means is that primary impedance should be selected for tone and desired output efficiency, that is, within constraints.

This is great stuff. I was speaking with George Metropolous (a living amp god) about the use of 4 x KT66 in the 100W Marshall amp platform and he schooled me on what I said regarding OT selection. I am building a modded Silver Jubilee-based amp with a Dagnall C1998 OT with adjustable bias, etc. He recommended a higher primary impedance OT than that if I wanted the 4 x KT66 badly enough. That would be the ideal, all else being the same. But like you said, the math can change everything!
 

DreamTheaterRules

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This is great stuff. I was speaking with George Metropolous (a living amp god) about the use of 4 x KT66 in the 100W Marshall amp platform and he schooled me on what I said regarding OT selection. I am building a modded Silver Jubilee-based amp with a Dagnall C1998 OT with adjustable bias, etc. He recommended a higher primary impedance OT than that if I wanted the 4 x KT66 badly enough. That would be the ideal, all else being the same. But like you said, the math can change everything!

I loved reading and learning about this stuff. I was headed to where you are now, but stopped before I got that far. I got to where I was planing JCM800 type builds before I finally had my awakening. This stuff is fascinating to me and I loved learning about it and then building something. But after a couple years, I realized I was spending WAY more time reading forums and books about building amps and pedals than I was actually playing guitars. I quit SO cold turkey that the last 4 times I've turned my soldering iron on, it was for a repair, not a build or mod. I still love to read a little about it and see what others are doing though.

I wish I had those 5 or more years back and had spent that time playing. My hand continues to get worse and eventually I won't be able to shred or play anything difficult and I could have waited til then to build stuff. :(
 

RickP

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I loved reading and learning about this stuff. I was headed to where you are now, but stopped before I got that far. I got to where I was planing JCM800 type builds before I finally had my awakening. This stuff is fascinating to me and I loved learning about it and then building something. But after a couple years, I realized I was spending WAY more time reading forums and books about building amps and pedals than I was actually playing guitars. I quit SO cold turkey that the last 4 times I've turned my soldering iron on, it was for a repair, not a build or mod. I still love to read a little about it and see what others are doing though.

I wish I had those 5 or more years back and had spent that time playing. My hand continues to get worse and eventually I won't be able to shred or play anything difficult and I could have waited til then to build stuff. :(
Always hard to look back at missed opportunities, but you were digging it then, so it wasn’t a loss. Those times of discovery are what keep my mind happy.
 

DreamTheaterRules

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Always hard to look back at missed opportunities, but you were digging it then, so it wasn’t a loss. Those times of discovery are what keep my mind happy.
Oh yeah, I enjoyed it while it was happening. Hind site is 20/20 though. If I'd had any idea that my hand would start to get progressively worse, I'd have spent that time playing. Of course, if it eventually locks me down to where I can hardly play, I won't want to be building guitar equipment anyway as that would be rubbing salt in a wound.
 

Em7

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Oh yeah, I enjoyed it while it was happening. Hind site is 20/20 though. If I'd had any idea that my hand would start to get progressively worse, I'd have spent that time playing. Of course, if it eventually locks me down to where I can hardly play, I won't want to be building guitar equipment anyway as that would be rubbing salt in a wound.

Between my vocation and my avocation, my hands have taken a beating. I have had carpel tunnel release surgery performed on both hands. There is no such thing as wasted knowledge. You now have insight that most guitarists do not possess. I think that Tom Scholz said it best when he was explaining the disconnect between engineers and musicians. Tom had the benefit of understanding the physics behind sound when he recorded Boston's debut album. Most people do not realize it, but Tom played every part of on the debut album other than drums and vocals. Knowledge is power. What we do with it defines our character.
 

DreamTheaterRules

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Between my vocation and my avocation, my hands have taken a beating. I have had carpel tunnel release surgery performed on both hands. There is no such thing as wasted knowledge. You now have insight that most guitarists do not possess. I think that Tom Scholz said it best when he was explaining the disconnect between engineers and musicians. Tom had the benefit of understanding the physics behind sound when he recorded Boston's debut album. Most people do not realize it, but Tom played every part of on the debut album other than drums and vocals. Knowledge is power. What we do with it defines our character.

Oh, I agree with all that. Just wish that all those nights I spent on BYOC, AX84 and SEWatt I had played for a while first.

My arthritis in my hand and ring finger of my left hand is from sports injuries. I had my ring finger dislocated like 4 times playing basketball. When the arthritis started to set in a few years ago, I almost had to cut my wedding ring off and have never been able to get it back on. The worse it gets, the less far I can bend it and the more stiff it is, and the less agile it is.

I also broke my left wrist and dislocated my left thumb. Both while playing basketball. I fear the day will come when I can’t play at all.
 
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