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Is a 12ax7 the same as an ECC83 or 7025?

Discussion in 'Amps and Cabs [BG]' started by Droog, Jan 20, 2004.


  1. Droog

    Droog

    Aug 14, 2003
    PDX
    I was just looking around at tubes and what have you. I play a 400+ and will have to change out the tubes eventually. I see 12ax7's and 7025's and ECC83's lumped together often are they all compatible?

    Also does anybody have experiance with Telefunken tubes? I love there mics, but do they make 12ax7's (or equivelent) or 6L6's? Thanks guys.
     
  2. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    Yes, a 7025 is just a 12AX7 that was tested for low noise I believe.
     
  3. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    They *made* 12AX7s--note past tense. They're pretty well thought of, and so the remaining ones carry a hefty price tag. I dunno if Telefunken ever made 6L6s. Certainly I've never seen or heard of any, but that doesn't mean a whole lot. It's conceivable that they may once have made an EL37, which is sorta the Euro equivalent of a 6L6, but I dunno about that either. The old 6L6s I hear the most about are GE and RCA, with a nod to the Tung-Sol 5881.

    You should try talking to some old tube mavens. Here's a link to Mike Kropotkin's site: www.kcanostubes.com
     
  4. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Telefunken's are okay for bass amps, maybe a little too dark for guitar amps though. No bite whatsoever (not like a Mullard).

    My 2c: don't waste your money on a Telefunken. They're fetching outrageous prices these days, even on eBay. And there's not so much difference that it would be obvious to an audience. If you like that sound, get an Ei Gold, they're current production tubes made in Yugoslavia, they're supposedly exact copies of the Telefunken and they sound just about the same.

    For NOS tubes, RCA's are still among the best. And they can be had new in the box for very reasonable prices. GE's are "not bad" either, they're kinda like a poor man's RCA.

    For current production, I like JJ's the best. They're pretty aggressive, but nicely balanced.
     
  5. Phat Ham

    Phat Ham

    Feb 13, 2000
    DC
    ECC83 is the European designation for 12AX7. Or you could think of it as 12AX7 being the American designation for an ECC83.
     
  6. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    I've been told that the Sovtek 12AX7LPS will get you in that Telefunken ballpark also and it sounds similar to the Ei Elite with the gold plating.
     
  7. Here's the breakdown, FWIW (let's see how I get flamed for this... :rolleyes: )

    12AX7- "standard" grade dual triode
    ECC83- European designation of same
    7025- A differently MADE 12AX7 with lower noise than standard


    Got gobs of Telefunkens; they're a VERY neutral sounding tube but have character to their tone. They don't work well in every bass amp because they also tend to have a significantly higher gain factor than most other 12AX7's. They're not noisier, just louder and will overdrive the first gain stage much easier. There isn't really anything out there that sounds like them. I have the Ei Golds as well, and they're thinner with less harmonic content and much worse microphonics. JJ Electronics are the BEST current 12AX7; they're like a woolier RCA and do have a certain amount of drive to the their sound.

    Telefunken never made a 6L6GC, because it's a beam tetrode design, which was developed by RCA in order to have a high power output tube without using pentode construction, whose patent was owned by Mullard and would have required licensing fees for RCA. The "EL" series of tubes are all high gain pentodes, and the later "KT" series were European tetrode copies of US designs. AFAIK, Telefunken ONLY made pentode output tubes.
     
  8. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    PBG is about right on.

    Quote from RCA manual re 7025:

    "This type is identical with miniature type 12AX7 except that it has a controlled equivalent noise and hum characteristic"

    Average hum and noise value is speced at 1.8 microvolts rms, max at 7 microvolts rms, (referenced to grid) in particular circuit conditions. The "max" is under different circuit conditions than the "average".

    I am not sure they actually made them differently vs selecting them. Some tubes Do have a military grade which is made differently. I was told by the "old tube guy" at one manufacturer that the 7025 was generally simply selected for. Certainly the "identical with" line implies they are made the same.....either way they are s'posed to be quieter.
     
  9. I think that the 7025 was designed atleast in part for Fender who needed a tube that wouldn't go microphonic in their combo amps atleast that is what I've heard.
     
  10. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD

    Yea, on the inside of my bassman, it says it needs 2 7025s.
     
  11. I'll have to go through my tube stock to check RCA and GE 7025's versus the 12AX7's, but with Sylvania 7025's v/ 12AX7's there is an entirely different plate and grid support structure as well as plate material. I have mil-spec Sylvania 7025's with green writing (JAN standard) and "normal" Sylvania 7025's with yellow writing that are identical. I'm more familar with the Sylvanias because I use them more. Philips bought out Sylvania and the JAN Philips 12AX7WA (best all around 12AX7 for bass, IMO) is just a later version of the Sylvania 7025, so if any of you don't want to pay big for the Philips JAN tube, just look for a Sylvania 7025.
     
  12. Droog

    Droog

    Aug 14, 2003
    PDX
    So where do JJ's fit into all this? Is JJ it's own company or are they actually RCA's with a different name? Reason I ask is because thats whats in my 400+, actually I have two Mesa's on channel two's pre-amp. I have been told the JJ stuff is the way to go and the amp sounds great, so I guess I will just stick to em'.

    On a side note, what do you all like for an old Bassman 70? I believe its a 70 or 71 not sure. Its my freind and I guess maybey the JJ stuff would work slick.
     
  13. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    JJ is a company in, I believe, the Slovak Republic that's making tubes *now*. (You can find out about them at www.eurotubes.com.) GE, RCA, Sylvania, Philips, et al aren't making tubes any more, so anything by them would be either (a) used or (b) new old stock (NOS), meaning that the tubes were made a while ago but happen never to have been used. So no, JJs aren't RCAs.
     
  14. For some more tube trivia, the Ei factory is an old Philips factory, even use the same boxes. JJ Electronics USED to be called Tesla tubes.
     
  15. JonB

    JonB

    May 27, 2003
    Indianapolis
    The 7025 has a coiled filament which is supposed to reduce hum in circuits using AC on the filaments. It was sold as a "lower noise" version of the 12ax7, but is identical in electrical characteristics. The new Sovtek 12ax7LPS is supposed to be the modern equivalent of the 7025.
    As someone else pointed out, probably the people at the bar won't notice the difference.
    BTW, EH 12AX7's sound pretty good, and are not very microphonic. (and they don't cost what good tele's do)
     
  16. kmacleish

    kmacleish

    Nov 19, 2003
    Atlanta, GA
    Hey, PBG -

    Is not the 6L6GC a beam power pentode? Never heard it referred to as a tetrode before, and my tube manual says pentode also.

    (NOTE: This is a request for clarification, not a flame. No flaming intent is intended. Should you experience a temperature increase, please check your thermostat, as it could not possibly be anything of a flaming-type nature from this message. No sirree. Not a chance. No flame here, you betcha.)
     
  17. It's neither a tetrode nor a pentode, it's a beam power tube. Could be called either one, though, depending on how you look at it, since it could be said to have 2 grids or 3 control elements. Just call it a beam power tube and forget it. :D

    And hey, you're in Atlanta? I'm an hour south of you down I-85. Neat.

    Chris
     
  18. kmacleish

    kmacleish

    Nov 19, 2003
    Atlanta, GA
    Hey, PBG -

    Is not the 6L6GC a beam power pentode? Never heard it referred to as a tetrode before, and my tube manual says pentode also.

    (NOTE: This is a request for clarification, not a flame. No flaming intent is intended. Should you experience a temperature increase, please check your thermostat, as it could not possibly be anything of a flaming-type nature from this message. No sirree. Not a chance. No flame here, you betcha.)
     
  19. Don't worry, this isn't a flame. It's a good question.

    The angle of grid pitch in a beam tetrode makes for a "virtual" third grid. Like throbbinut said, in the circuit, it can be either, but in the strict sense, it is a beam tetrode, which was a "cheater" way to get high power pentode performance and not have to pay royalties to Mullard. It's NOT a true pentode and it does make a difference. The EL34 is a pentode. The 6CA7 is its electronic equivalent, but in beam tetrode form. Both bias pretty close, and both handle similar voltages by design, but there is a BIG difference in sound between the two.
     
  20. Droog

    Droog

    Aug 14, 2003
    PDX
    I am not fully clear on what Bias is in relation to tubes. Is it similiar the the bias of a tape machine? Thats why I am confused.