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Ok guys, here's the big tube type hoedown. All information below is my opinion only - the tone/sounds of the tubes is how I perceived em in a THD Univalve and also in my own custom amps that allow tube swaps.
12ax7 - the typical preamp tube in most guitar amps sold today. These are the smallest tubes in your amp, and they usually last the longest. A 7025 used to be the high quality version, and a ECC83 was the European name for a 12ax7. Neither mean much today, as any tube manufacturer can and will use the terms interchangeably. Each of the preamp tubes listed below are actually *two* gain stages in one glass envelope. This is why an amp that has 6 gain stages doesn't have to have 6 tubes in the preamp - it may just have 3.
5751 - Industrial 12ax7 tube, lower noise, lower gain. Great for thickening up the tone of an amp that has too much gain.
12au7 - can be used in place of a 12ax7 for lower gain. Usually used as reverb drivers or phase inverters. These can also be used as power tubes - I have a 2 watt amp that runs one. Quite loud for what it is!
12at7 - used mostly in old fenders, hardly ever used today.
12dw7 - one side is a 12ax7, other side is a 12au7. Used in some old Ampegs I believe... good for cutting the gain on your amp on one gain stage. Other than that, not real useful for most of us. I doubt many guys here on the JCF think of anything having 'too much gain'.
6V6 - lower powered tube, has the same look as a 6L6 but shorter. Sounds a lot like one too, with one very important difference: It distorts much earlier/easier, and gives out quite a bit less wattage. They also will die at typical 6L6GC voltages. The Univalve will run one of these in the 'low voltage' setting - use the normal setting for the voltage and your 6V6 will go Chernobyl on you. These tubes were used in many smaller 'student' amps in the 50s and 60s and also a few others. Most famous amps I can think of that used 6V6 power tubes were Fender Champs (tweed, BF and SF) and also Fender Princetons. Oh, and some weird little power amp built by Twister amps. [img]images/icons/grin.gif[/img]
EL84 - another lower powered tube. This guy uses the same shape socket as a preamp tube, but is a little taller. Sounds a lot like a small EL34, but they distort much easier and more than an EL34. This is a GREAT power tube if you're looking for a small marshall sound with excellent crunch at fairly low volumes. Marshall briefly made an 18 watt amp that used a pair of EL84s in the 60s (that are worth crazy money now... a big thing currently is to clone em) and the DSL20 and 40 series I believe uses them for power tubes. Other notable amps that used these: Vox AC30, Mesa Studio .22+, Peavey Classic 30 and 50 series heads.
6L6. several variants - 6L6G, GA, GB, GC - as you go towards the GC, power ratings and handling goes up. A 5881 used to be a militarized version of the GB - nowadays it's a stout 6L6 type. The GC takes a lot of voltage and gives back lots of tone. A 6L6GC sounds slightly scooped to me - big bottom, clean highs, but a slightly hollow tone. Most Fender amps used 6L6 tubes, and this is likely the most popular power tube for guitar amps. These tubes do not overdrive as easily as the 6V6s, and stay tighter much longer.
EL34. Marshalls started using these in their amps because they couldn't get 6L6s easily, and EL34s were a british made tube. These take more voltage than a 6L6 can, and also need more filament current. An EL34 has a nice midrange, and gets a crunchier tone than the 6L6s. These were the Marshall tube for the longest time, and also Hiwatts used them. If you own an amp that can swap between the tube types (like a mesa recto head) the EL34s will give you more complex mids, slightly less highs and lows, but a terrific European-style crunch. The 6L6s will get you a cleaner more percussive sound but not as much midrange punch. Either sound great, I gravitate personally towards the 34s.
6550/KT88 - These are the bad boys. Any amp that runs EL34s can be rebiased to take a set of these, but it's likely you won't see much wattage increase unless the amp was designed FOR these tubes in the first place. KT88/6550s have a solid bottom and are harder than hell to distort - a power amp built with these will give pummeling tones. Some VHT power amps use these, also crazily high powered amps like the Fender 400 (yes, 400 watts, all tube) and the *cough* Crate BV300 head. Also some Ampeg SVT heads. These tubes are also very expensive new even for the cheaper imports and are wide in the middle like a coke bottle.
My recommendations for tubes, in no particular order:
12ax7/preamp Vintage - RCA7025, Mullard (any), Telefunken, GE, Sylvania, just about any USA or British Tube
12ax7/preamp new: Electro Harmonix, Chinese Silver Special (early chinese, crazy high gain, some won't fit into some amps because some are a little wider than regular tubes), Chinese 12ax7C, JJs
6V6 - any vintage USA, with RCA blackplates and JAN 107-As leading the list.
New: I don't like any of them, but the new EH is supposed to be good.Vintage 6V6s are still cheap enough that I'd recommend old tubes.
EL84, vintage - Telefunken, Mullard, GE, RCA
new - EH, Sovtek. Both have a different tone, and the Sovteks are really cool sounding.
6L6 and family - Vintage: TungSol 5881, GE, Phillips, Sylvania, RCA
New: Groove Tubes 6L6G? (the usa one... sounds great, but pricey!) Svetlanas, the Sovtek 5881WXT
EL34:
Vintage - Mullard (take a 2nd mortgage out to get a matched quad NOS), Siemens, Audio Glassic
New - JJs are pretty good, so are Svetlanas.
Really, there isn't such a thing as a 'bad' tube - some just have better characteristics than others. A player may want an RCA 7025 to give their amp more brightness, or a 12ax7EH to tame some hiss/high end. Also remember that some amps like some types of tubes better... some high gain preamps sound best with newer tubes, some vintage amps sound TERRIBLE with newer tubes. The best thing to do is experiment. Especially if you have an expensive amp, what's $100 or so checking out the possibilities?
If you guys have any questions, feel free to email me at [email protected].
Pete
12ax7 - the typical preamp tube in most guitar amps sold today. These are the smallest tubes in your amp, and they usually last the longest. A 7025 used to be the high quality version, and a ECC83 was the European name for a 12ax7. Neither mean much today, as any tube manufacturer can and will use the terms interchangeably. Each of the preamp tubes listed below are actually *two* gain stages in one glass envelope. This is why an amp that has 6 gain stages doesn't have to have 6 tubes in the preamp - it may just have 3.
5751 - Industrial 12ax7 tube, lower noise, lower gain. Great for thickening up the tone of an amp that has too much gain.
12au7 - can be used in place of a 12ax7 for lower gain. Usually used as reverb drivers or phase inverters. These can also be used as power tubes - I have a 2 watt amp that runs one. Quite loud for what it is!
12at7 - used mostly in old fenders, hardly ever used today.
12dw7 - one side is a 12ax7, other side is a 12au7. Used in some old Ampegs I believe... good for cutting the gain on your amp on one gain stage. Other than that, not real useful for most of us. I doubt many guys here on the JCF think of anything having 'too much gain'.
6V6 - lower powered tube, has the same look as a 6L6 but shorter. Sounds a lot like one too, with one very important difference: It distorts much earlier/easier, and gives out quite a bit less wattage. They also will die at typical 6L6GC voltages. The Univalve will run one of these in the 'low voltage' setting - use the normal setting for the voltage and your 6V6 will go Chernobyl on you. These tubes were used in many smaller 'student' amps in the 50s and 60s and also a few others. Most famous amps I can think of that used 6V6 power tubes were Fender Champs (tweed, BF and SF) and also Fender Princetons. Oh, and some weird little power amp built by Twister amps. [img]images/icons/grin.gif[/img]
EL84 - another lower powered tube. This guy uses the same shape socket as a preamp tube, but is a little taller. Sounds a lot like a small EL34, but they distort much easier and more than an EL34. This is a GREAT power tube if you're looking for a small marshall sound with excellent crunch at fairly low volumes. Marshall briefly made an 18 watt amp that used a pair of EL84s in the 60s (that are worth crazy money now... a big thing currently is to clone em) and the DSL20 and 40 series I believe uses them for power tubes. Other notable amps that used these: Vox AC30, Mesa Studio .22+, Peavey Classic 30 and 50 series heads.
6L6. several variants - 6L6G, GA, GB, GC - as you go towards the GC, power ratings and handling goes up. A 5881 used to be a militarized version of the GB - nowadays it's a stout 6L6 type. The GC takes a lot of voltage and gives back lots of tone. A 6L6GC sounds slightly scooped to me - big bottom, clean highs, but a slightly hollow tone. Most Fender amps used 6L6 tubes, and this is likely the most popular power tube for guitar amps. These tubes do not overdrive as easily as the 6V6s, and stay tighter much longer.
EL34. Marshalls started using these in their amps because they couldn't get 6L6s easily, and EL34s were a british made tube. These take more voltage than a 6L6 can, and also need more filament current. An EL34 has a nice midrange, and gets a crunchier tone than the 6L6s. These were the Marshall tube for the longest time, and also Hiwatts used them. If you own an amp that can swap between the tube types (like a mesa recto head) the EL34s will give you more complex mids, slightly less highs and lows, but a terrific European-style crunch. The 6L6s will get you a cleaner more percussive sound but not as much midrange punch. Either sound great, I gravitate personally towards the 34s.
6550/KT88 - These are the bad boys. Any amp that runs EL34s can be rebiased to take a set of these, but it's likely you won't see much wattage increase unless the amp was designed FOR these tubes in the first place. KT88/6550s have a solid bottom and are harder than hell to distort - a power amp built with these will give pummeling tones. Some VHT power amps use these, also crazily high powered amps like the Fender 400 (yes, 400 watts, all tube) and the *cough* Crate BV300 head. Also some Ampeg SVT heads. These tubes are also very expensive new even for the cheaper imports and are wide in the middle like a coke bottle.
My recommendations for tubes, in no particular order:
12ax7/preamp Vintage - RCA7025, Mullard (any), Telefunken, GE, Sylvania, just about any USA or British Tube
12ax7/preamp new: Electro Harmonix, Chinese Silver Special (early chinese, crazy high gain, some won't fit into some amps because some are a little wider than regular tubes), Chinese 12ax7C, JJs
6V6 - any vintage USA, with RCA blackplates and JAN 107-As leading the list.
New: I don't like any of them, but the new EH is supposed to be good.Vintage 6V6s are still cheap enough that I'd recommend old tubes.
EL84, vintage - Telefunken, Mullard, GE, RCA
new - EH, Sovtek. Both have a different tone, and the Sovteks are really cool sounding.
6L6 and family - Vintage: TungSol 5881, GE, Phillips, Sylvania, RCA
New: Groove Tubes 6L6G? (the usa one... sounds great, but pricey!) Svetlanas, the Sovtek 5881WXT
EL34:
Vintage - Mullard (take a 2nd mortgage out to get a matched quad NOS), Siemens, Audio Glassic
New - JJs are pretty good, so are Svetlanas.
Really, there isn't such a thing as a 'bad' tube - some just have better characteristics than others. A player may want an RCA 7025 to give their amp more brightness, or a 12ax7EH to tame some hiss/high end. Also remember that some amps like some types of tubes better... some high gain preamps sound best with newer tubes, some vintage amps sound TERRIBLE with newer tubes. The best thing to do is experiment. Especially if you have an expensive amp, what's $100 or so checking out the possibilities?
If you guys have any questions, feel free to email me at [email protected].
Pete
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