Hi guys,
I know this seem stupid but could you tell me what the difference is between different types of tubes (e.g. EL-34, KT-66 etc.)?
Also how hard is it to switch between different types of tubes?
Thanks for any info,
Lawrence
Tube info
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bluefuzzguitar
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No question is stupid as long as they're posted by a real Metro Amp forumite instead of our 'Guest' who pops up every once in a while with some really stupid shit.
What sort of info are you looking for, Lawrence? Do you need descriptions of what the tubes sound like or technical info like pentode vs triode and stuff like that?
Mike
What sort of info are you looking for, Lawrence? Do you need descriptions of what the tubes sound like or technical info like pentode vs triode and stuff like that?
Mike
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bluefuzzguitar
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Awright, here goes. I don't know anything about the pentode/triode difference but I do know what different power tubes sound like, so here's a crummy description of each tube from a player's point of view.
Basically I can distinguish 8 types of end tubes that will fit in a Marshall plexi no problem, each with their own characteristics in sound, feel and response: EL34, 6CA7, 6L6, 7581A, 5881, KT66, KT88, 6550.
EL34: Current-production EL34's are designed to give you that midrange crunch rock music is known for. I never had the pleasure of hearing a new old stock or used old stock EL34 (Mullard) but from the descriptions George has given on this forum they sound warmer and more versatile than the newer EL34's. They are also cleaner with more headroom, which means that when they break up or are pushed by pedals the sound still doesn't get overly compressed or saturated. I find most current-production EL34's to be good only at producing that middy grind. They break up early and most of them tend to get shrill in the high end. The general consensus seems to be that the Svetlana EL34 and the JJ EL34L are the best new EL34's. I personally find the EL34's to be too much of a one-trick-pony for my taste but if you're looking for the classic 70's and 80's rock sound then EL34's are definitely the way to go.
6CA7: The term 6CA7 is often used synonymously with EL34. This is not correct as a true 6CA7 is an American big-bottle version of the British EL34 design. I don't know how it works exactly but from what I understand the 6CA7 is the basic EL34 design but with an added element of the American 6L6 design. The only decent new-production 6CA7 IMO is the GT-6CA7GE (remake of the General Electrics 6CA7 - yes, the one EVH used!). I own some original GE 6CA7's and I would describe them as a cleaner version of an EL34 which is slightly more American-sounding (i.e. more midscooped, less midrange grind, cleaner with more headroom, later breakup). The main feature of the big-bottle 6CA7 is its HUGE dark and tight low end response while still retaining its brightness. This tube is often used by bass players but you guitar players looking for a tube with lots of warm, clean output without sounding sterile might like it too. A very musical tube which is great for use in combination with pedals or heavy preamp gain because of their tight sound and clean headroom.
6L6: The tube you associate with Fender amps. The classic American tube sound: lots of lows and highs, midrange is not so well pronounced. The slightly midscooped quality of a 6L6 gives it its sweet and round 'glassy' character. The 6L6 is less 'forward-sounding' than a British tube like the EL34, yet in return you get a very sparkly tube with bell-like highs. The lows can get muddy when pushed so if you're gonna go for 6L6's in your Marshall I suggest you choose the 6L6GC which has a slightly higher output than a regular 6L6 and will sound tighter due to its increased headroom, especially in the low-end department. Best current-production 6L6's IMO are the JJ's and Svetlana's. I hear the GT-6L6GE (Groove Tubes replica of the GE 6L6) is very good too.
7581A: This is the military version of the 6L6GC, in other words a 'harder' tube (even cleaner and tighter). Expect HUGE low end and sweet, glassy, bell-like highs. This tube has all the qualities of a 6L6, only enhanced due to its bigger headroom. This tube is also favored by bass players but guitarists looking for the American midscooped 6L6 sound with later breakup will love it too. Great for use with pedals or heavy preamp gain to keep your sound nice and tight without it getting muddy when pushed. Unfortunately there's no current-production version of the 7581A on the market today so you'll have to look for NOS ones made by American companies like GE and RCA. They show up regularly on eBay and if you bid smart you can get them for decent $. The 7581A is often called the American KT66 because it's similar in design to that British tube. The 7581A does sound distinctly American (less pronounced mids), tho, whereas the KT66 sounds British (more pronounced mids).
5881: Also called the 6L6WGB and NOT the 6L6GC as they are often referred to. You guessed it, the 5881 is another version of a 6L6. This time, tho, it actually has a LOWER output with LESS headroom. Great for guitarists seeking the classic midscooped American sound with early breakup. Has a tendency to get muddy in the lows and shouldn't be pushed too hard. Not my favorite 6L6-type tube.
KT66: The British equivalent of the 6L6 design. The difference being they eliminated the mid 'kink', that slightly midscooped quality that gives the 6L6 its sweet and round character. KT stands for Kinkless Triode. What the KT66 gives you in return is a more pronounced and wider midrange and more clean headroom. The KT66 is capable of producing a midrange crunch which is similar to an EL34, yet it's considered a more versatile and musical tube. It's the perfect tube if you're looking for a hybrid British/American sound, i.e. the middy grind associated with British amps (Marshall, Vox, Hiwatt, Orange, etc.) coupled with the clean glassiness of American amps (Fender, early Mesa Boogies, etc.). The best KT66 ever is the GEC (Genelex). These go for hundreds of dollars on eBay. Best current-production, according to many, is the GT-KT66HP (Russian-made KT66 designed exclusively for Groove Tubes). Sounds great with pedals.
KT88: The British version of the American 6550 design. Again the mid 'kink' is eliminated, giving you a broader, more dynamic midrange. This tube has HUGE headroom and sounds darker than the KT66 because it enhances the lower frequencies especially. This is why the KT88 is liked by bassists. Guitarists looking for that extra bit of OOMPH! in their sound use either KT88's or 6550's depending on how much midrange they want their preferred sound to have. Again the GEC KT88 is considered the ultimate KT88 which explains their high $ value. Best current-production KT88 is without a doubt the JJ KT88.
6550: If you like the American 6L6 type of sound but you need even more clean headroom than a 7581A then a 6550 is what you want. These tubes sound very stiff and will take any kind of abuse gladly and not even blink an eye, which is great if you're looking for maximum clean headroom in a tube. On the other hand, the 6550 is less musical than its British counterpart the KT88 because of its less pronounced midrange. This causes the 6550 to always respond in a very stiff manner no matter how hard you dig in on your guitar. Bass players love this tube. Most guitarists will prefer the KT88 over the 6550. Yet it's a great tube for guitar if you're into HUGE clean output, especially in combination with heavy preamp gain (Zakk Wylde, Slash). Best current-production 6550 IMHO is the Svetlana 6550-C.
There you have it, Lawrence, the 8 tubes as best I can describe them. One is not better than the other, just different flavors. It really depends on what type of sound you have in mind. These descriptions are meant to help you distinguish between the various power tubes that are available. If I have inadvertenly confused you all the more then by all means describe the type of sound you want out of your amp and I'll try to match it with a certain tube. Maybe some of the others can describe the technical aspects (tube construction, layout, build quality, etc.)?
Mike
Basically I can distinguish 8 types of end tubes that will fit in a Marshall plexi no problem, each with their own characteristics in sound, feel and response: EL34, 6CA7, 6L6, 7581A, 5881, KT66, KT88, 6550.
EL34: Current-production EL34's are designed to give you that midrange crunch rock music is known for. I never had the pleasure of hearing a new old stock or used old stock EL34 (Mullard) but from the descriptions George has given on this forum they sound warmer and more versatile than the newer EL34's. They are also cleaner with more headroom, which means that when they break up or are pushed by pedals the sound still doesn't get overly compressed or saturated. I find most current-production EL34's to be good only at producing that middy grind. They break up early and most of them tend to get shrill in the high end. The general consensus seems to be that the Svetlana EL34 and the JJ EL34L are the best new EL34's. I personally find the EL34's to be too much of a one-trick-pony for my taste but if you're looking for the classic 70's and 80's rock sound then EL34's are definitely the way to go.
6CA7: The term 6CA7 is often used synonymously with EL34. This is not correct as a true 6CA7 is an American big-bottle version of the British EL34 design. I don't know how it works exactly but from what I understand the 6CA7 is the basic EL34 design but with an added element of the American 6L6 design. The only decent new-production 6CA7 IMO is the GT-6CA7GE (remake of the General Electrics 6CA7 - yes, the one EVH used!). I own some original GE 6CA7's and I would describe them as a cleaner version of an EL34 which is slightly more American-sounding (i.e. more midscooped, less midrange grind, cleaner with more headroom, later breakup). The main feature of the big-bottle 6CA7 is its HUGE dark and tight low end response while still retaining its brightness. This tube is often used by bass players but you guitar players looking for a tube with lots of warm, clean output without sounding sterile might like it too. A very musical tube which is great for use in combination with pedals or heavy preamp gain because of their tight sound and clean headroom.
6L6: The tube you associate with Fender amps. The classic American tube sound: lots of lows and highs, midrange is not so well pronounced. The slightly midscooped quality of a 6L6 gives it its sweet and round 'glassy' character. The 6L6 is less 'forward-sounding' than a British tube like the EL34, yet in return you get a very sparkly tube with bell-like highs. The lows can get muddy when pushed so if you're gonna go for 6L6's in your Marshall I suggest you choose the 6L6GC which has a slightly higher output than a regular 6L6 and will sound tighter due to its increased headroom, especially in the low-end department. Best current-production 6L6's IMO are the JJ's and Svetlana's. I hear the GT-6L6GE (Groove Tubes replica of the GE 6L6) is very good too.
7581A: This is the military version of the 6L6GC, in other words a 'harder' tube (even cleaner and tighter). Expect HUGE low end and sweet, glassy, bell-like highs. This tube has all the qualities of a 6L6, only enhanced due to its bigger headroom. This tube is also favored by bass players but guitarists looking for the American midscooped 6L6 sound with later breakup will love it too. Great for use with pedals or heavy preamp gain to keep your sound nice and tight without it getting muddy when pushed. Unfortunately there's no current-production version of the 7581A on the market today so you'll have to look for NOS ones made by American companies like GE and RCA. They show up regularly on eBay and if you bid smart you can get them for decent $. The 7581A is often called the American KT66 because it's similar in design to that British tube. The 7581A does sound distinctly American (less pronounced mids), tho, whereas the KT66 sounds British (more pronounced mids).
5881: Also called the 6L6WGB and NOT the 6L6GC as they are often referred to. You guessed it, the 5881 is another version of a 6L6. This time, tho, it actually has a LOWER output with LESS headroom. Great for guitarists seeking the classic midscooped American sound with early breakup. Has a tendency to get muddy in the lows and shouldn't be pushed too hard. Not my favorite 6L6-type tube.
KT66: The British equivalent of the 6L6 design. The difference being they eliminated the mid 'kink', that slightly midscooped quality that gives the 6L6 its sweet and round character. KT stands for Kinkless Triode. What the KT66 gives you in return is a more pronounced and wider midrange and more clean headroom. The KT66 is capable of producing a midrange crunch which is similar to an EL34, yet it's considered a more versatile and musical tube. It's the perfect tube if you're looking for a hybrid British/American sound, i.e. the middy grind associated with British amps (Marshall, Vox, Hiwatt, Orange, etc.) coupled with the clean glassiness of American amps (Fender, early Mesa Boogies, etc.). The best KT66 ever is the GEC (Genelex). These go for hundreds of dollars on eBay. Best current-production, according to many, is the GT-KT66HP (Russian-made KT66 designed exclusively for Groove Tubes). Sounds great with pedals.
KT88: The British version of the American 6550 design. Again the mid 'kink' is eliminated, giving you a broader, more dynamic midrange. This tube has HUGE headroom and sounds darker than the KT66 because it enhances the lower frequencies especially. This is why the KT88 is liked by bassists. Guitarists looking for that extra bit of OOMPH! in their sound use either KT88's or 6550's depending on how much midrange they want their preferred sound to have. Again the GEC KT88 is considered the ultimate KT88 which explains their high $ value. Best current-production KT88 is without a doubt the JJ KT88.
6550: If you like the American 6L6 type of sound but you need even more clean headroom than a 7581A then a 6550 is what you want. These tubes sound very stiff and will take any kind of abuse gladly and not even blink an eye, which is great if you're looking for maximum clean headroom in a tube. On the other hand, the 6550 is less musical than its British counterpart the KT88 because of its less pronounced midrange. This causes the 6550 to always respond in a very stiff manner no matter how hard you dig in on your guitar. Bass players love this tube. Most guitarists will prefer the KT88 over the 6550. Yet it's a great tube for guitar if you're into HUGE clean output, especially in combination with heavy preamp gain (Zakk Wylde, Slash). Best current-production 6550 IMHO is the Svetlana 6550-C.
There you have it, Lawrence, the 8 tubes as best I can describe them. One is not better than the other, just different flavors. It really depends on what type of sound you have in mind. These descriptions are meant to help you distinguish between the various power tubes that are available. If I have inadvertenly confused you all the more then by all means describe the type of sound you want out of your amp and I'll try to match it with a certain tube. Maybe some of the others can describe the technical aspects (tube construction, layout, build quality, etc.)?
Mike
Last edited by bluefuzzguitar on Tue Jun 29, 2004 5:47 am, edited 3 times in total.
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Country Boy Shane
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Excellent descriptions Mike. I should make this thread a sticky for your post alone.
But, right now I can't even seem to log in EEEERRRRR!!!!
Let me add my impression of EL-34's.
Mullards have a reputation for being "clean" or "punchy" or "sweet" or whatever adjective might be used to describe them because, for the most part, they have a flat frequency response.
Actually, I should say they have a flatter frequency response than current manufacture EL-34's.
This flat response makes the mids seem punchy and present compared to modern tubes. It makes Mullards seem and feel cleaner at most settings because the lows don't fart out and the highs don't get piercing.
As for modern tubes, they each seem to exhibit some Mullard like qualities. But, unfortunately, none really capture the essence of Mullards completely.
A few observations:
JJ/Tesla truly a great EL-34. Very pronounced in the mid range and great upper-mid grind. Somewhat lacking in the lower frequencies, which is perfect for some amps (like superbass circuits).
Winged "C" (formerly Svetlana): another great EL-34, but with distinctly different characteristics than JJ's.
These tubes are punchy and feel cleaner. But with a sometimes over-emphasized low end. The mids are less pronounced and the highs are ever present. Still a very musical tube, but not suited for already bassy amps.
Electro-Harmonix (which is really just a premium re-labled Sovtek): These too are really good EL-34's. They even claim to sound most like a MUllard!
While I do hear a certain flatness to them, it's not the same as in the Mullards. It's a more sterile flatness. Nothing is really over-emphasized, almost to a fault. The highs are on par with the other current EL-34's in my opinion. These are pretty robust and reliable tubes.
I try to utilize the tubes that will compliment each amp I work on best, and these have been the ticket in the fewest Marshall type amps of the three brands I've listed.
Of course, these things are all subjective. So please, take them for what they're worth. They're just my observations.
George
But, right now I can't even seem to log in EEEERRRRR!!!!
Let me add my impression of EL-34's.
Mullards have a reputation for being "clean" or "punchy" or "sweet" or whatever adjective might be used to describe them because, for the most part, they have a flat frequency response.
Actually, I should say they have a flatter frequency response than current manufacture EL-34's.
This flat response makes the mids seem punchy and present compared to modern tubes. It makes Mullards seem and feel cleaner at most settings because the lows don't fart out and the highs don't get piercing.
As for modern tubes, they each seem to exhibit some Mullard like qualities. But, unfortunately, none really capture the essence of Mullards completely.
A few observations:
JJ/Tesla truly a great EL-34. Very pronounced in the mid range and great upper-mid grind. Somewhat lacking in the lower frequencies, which is perfect for some amps (like superbass circuits).
Winged "C" (formerly Svetlana): another great EL-34, but with distinctly different characteristics than JJ's.
These tubes are punchy and feel cleaner. But with a sometimes over-emphasized low end. The mids are less pronounced and the highs are ever present. Still a very musical tube, but not suited for already bassy amps.
Electro-Harmonix (which is really just a premium re-labled Sovtek): These too are really good EL-34's. They even claim to sound most like a MUllard!
While I do hear a certain flatness to them, it's not the same as in the Mullards. It's a more sterile flatness. Nothing is really over-emphasized, almost to a fault. The highs are on par with the other current EL-34's in my opinion. These are pretty robust and reliable tubes.
I try to utilize the tubes that will compliment each amp I work on best, and these have been the ticket in the fewest Marshall type amps of the three brands I've listed.
Of course, these things are all subjective. So please, take them for what they're worth. They're just my observations.
George
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bluefuzzguitar
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Correct me if I'm wrong here, George, but didn't you discover recently that the Russian GT KT66's sound more like a Mullard EL34 than all of the current-production EL34's put together? Or is this an overstatement?
My personal faves:
If you're looking for a British EL34-type sound go for the 6CA7.
If you're looking for an American 6L6-type sound go for the 7581A or the 6550. Although they are similar in output there's a marked difference in response: I consider the 7581A to be a much more musical tube than the 6550, i.e. the 7581A shows much more dynamics ('works' with your pick attack and pedals) than the 6550.
If you're looking for a hybrid British/American sound go for the KT66 or KT88, the KT66 being the most dynamic of the two. I guess you could consider the 6CA7 to be a hybrid of sorts too as it is an EL34 fused with a 6L6.
Mike
My personal faves:
If you're looking for a British EL34-type sound go for the 6CA7.
If you're looking for an American 6L6-type sound go for the 7581A or the 6550. Although they are similar in output there's a marked difference in response: I consider the 7581A to be a much more musical tube than the 6550, i.e. the 7581A shows much more dynamics ('works' with your pick attack and pedals) than the 6550.
If you're looking for a hybrid British/American sound go for the KT66 or KT88, the KT66 being the most dynamic of the two. I guess you could consider the 6CA7 to be a hybrid of sorts too as it is an EL34 fused with a 6L6.
Mike
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martin g
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Hello Thanks for this post.
I've started with my 69 super lead (since month), with 4*12 greenback cab. I've got a question about power tubes. I have to change my power tubes and I hesitate to stay with el 34 or change to other else? I play on single coil startocaster and never experiment with other types of power tubes. I'm looking for powerfull stratocaster bell sound but don't loose marshall's drive sound, something between fender amp and marshall. Is it possible?
Thanks Martin
I've started with my 69 super lead (since month), with 4*12 greenback cab. I've got a question about power tubes. I have to change my power tubes and I hesitate to stay with el 34 or change to other else? I play on single coil startocaster and never experiment with other types of power tubes. I'm looking for powerfull stratocaster bell sound but don't loose marshall's drive sound, something between fender amp and marshall. Is it possible?
Thanks Martin
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Billy Batz
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Gtr_tech
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Some corrections to the Tube Info post:
The English "KT" prefixed tubes are Kinkless Tetrodes, not triodes.
The "kink" that was removed does not refer to an audible quality, but to the plate current graphs through thier operating range. This imperfection, or "kink" was caused by secondary emission from the screen grid. The advent of beam forming plates to replace the suppressor in a standard pentode brought about the new kinkless tetrode. Not counting the beam plates as tube elements causes some to refer to them as tetrodes.
Americans called them "beam power tubes".
The English "KT" prefixed tubes are Kinkless Tetrodes, not triodes.
The "kink" that was removed does not refer to an audible quality, but to the plate current graphs through thier operating range. This imperfection, or "kink" was caused by secondary emission from the screen grid. The advent of beam forming plates to replace the suppressor in a standard pentode brought about the new kinkless tetrode. Not counting the beam plates as tube elements causes some to refer to them as tetrodes.
Americans called them "beam power tubes".
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martin g
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bluefuzzguitar
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[quote="martin g"]Hello Thanks for this post.
I've started with my 69 super lead (since month), with 4*12 greenback cab. I've got a question about power tubes. I have to change my power tubes and I hesitate to stay with el 34 or change to other else? I play on single coil startocaster and never experiment with other types of power tubes. I'm looking for powerfull stratocaster bell sound but don't loose marshall's drive sound, something between fender amp and marshall. Is it possible?
Thanks Martin[/quote]
Martin,
From your description I'd say either 6CA7's or KT66's will do the trick. You first need to decide whether you want your tubes to sound more like an EL34 or a 6L6. If you like the sound of EL34's but want a bit more bell-like clarity and headroom I'd say go for Groove Tubes 6CA7's. If you want your tubes to sound more like a 6L6 Fender-type sound with some good old British mid grind, go for the KT66. I recommend the GTKT66HP. Hope this helps.
Mike
I've started with my 69 super lead (since month), with 4*12 greenback cab. I've got a question about power tubes. I have to change my power tubes and I hesitate to stay with el 34 or change to other else? I play on single coil startocaster and never experiment with other types of power tubes. I'm looking for powerfull stratocaster bell sound but don't loose marshall's drive sound, something between fender amp and marshall. Is it possible?
Thanks Martin[/quote]
Martin,
From your description I'd say either 6CA7's or KT66's will do the trick. You first need to decide whether you want your tubes to sound more like an EL34 or a 6L6. If you like the sound of EL34's but want a bit more bell-like clarity and headroom I'd say go for Groove Tubes 6CA7's. If you want your tubes to sound more like a 6L6 Fender-type sound with some good old British mid grind, go for the KT66. I recommend the GTKT66HP. Hope this helps.
Mike
There's no tone like your own