1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

12AX7 bass preamp tubes Favorites and Lifespan

Discussion in 'Amps and Cabs [BG]' started by Phat Ham, Jan 24, 2001.

  1. Phat Ham

    Phat Ham

    Feb 13, 2000
    I was bored one day and took apart my Carvin R600 head and found a sovtek 12AX7 preamp tube in it. Then I took apart my Digitech BP8 and found a Sovtek in that too. I know close to nothing about tubes and was wondering if these are good tubes or if I could get a better sound out of better tubes. If anyone has suggestions please let me know.

    woohoo! I just realized I become a senior member with this post.
    Pbassmanca likes this.
  2. Doug


    Apr 5, 2000
    Buffalo, N.Y.
    IMO, the Sovtek 12AX7's are ok. Personally I prefer NOS(New Old Stock) preamp tubes like Phillips, RCA, or Telefunkens, which are my favorite. JJ/Tesla 12AX7 tubes are my favorite current production preamp tube. Prices can vary on these tubes. Usually between $5-$15/tube. However, preamp tubes like Telefunkens, Mullards, Tungsol, and Amperex can go for $30-$90. Each brand will sound tonally different than the other. The only way to judge is try some out in your particuliar amp. You can also substitute other types for less gain if you want. A 12AU7 can be used for less gain and a little cleaner sound. For even lesser gain try a 12AT7.

    Here's a link to a tube dealer. Check it out. Go to the 12AX7 and 12AU7 sections. You can get an idea of what these go for and there is also a brief description of the different manufacturers tube. Hope this helps.

  3. Another link:


    You may get some difference by plugging in a different 12Ax7 brand. Won't be night and day difference, unless the ones you have are bad or something, which they probably aren't.

  4. I have my Eden Navigator next to me now with the top off. I'm doing the same thing. It came with a Sovtek 12AX7WA in it. Very clear & crisp. Maybe a little too much, but notes are very defined. A Jan PhillipsECG 12AX7WA has the same definition, but with more warmth. Same gain. The next best is a Sylvania 12AX7/ECC83/7025 About the sam, less definition-good warmth.GE 12AX7/7025, less definition, more warmth. RCA 12AX7, Same. Mullard ECC83, Great tone. A guitar tube, not bass, unless you like high gain, easy distortion. I play too hard for this tube.

    My vote is in the order above. I'm still switching back & forth between the Phillips & Sylvania.
  5. Phat Ham

    Phat Ham

    Feb 13, 2000
    One more thing. If I do get a different tube to put in can I just pull out the old one and slide in a new one? Or is there a certain process involved in changing the tubes?
  6. Preamp tubes can be changed with nothing else to do, unlike power tubes which need to be matched and biased.
  7. Phat Ham

    Phat Ham

    Feb 13, 2000
    I guess I should have been more specific. I mean when I change the tube can I just physically yank out the tube or do I have to unscrew something or what?
  8. Doug


    Apr 5, 2000
    Buffalo, N.Y.
    You should be able to just gently wiggle the tube out with no problem. Then just slide the new one in, lining up the pins. That's it!
  9. I recently bought a guitar amp (sorry :D)
    and it says it has a tube pre-amp and a solid state power amp section. It's a small Marshall. While reading the owner's manual, I noticed it didn't say anything about replacing the pre amp tube, so my question is: Will this thing never burn out, or is there some new technology that I'm not aware of ?
    It says the tube is an ECC038 or something to that effect, and they compare it to a 12AX7.

    BTW, it sounds dynamite. I read the manual carefully, and it says there are no user serviceable parts inside. There is not one word about replacing the tube.

    Any help appreciated.
    Mike J.
  10. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    If it's an ECC83 then it's the European version of the 12AX7.
    Preamp tubes usually last almost forever, if it works and sounds fine you can keep it in there.

    That sign is there for warranty and safety reasons.
    You can replace it yourself if you are good with things like this. Ruby Tubes, Groove Tubes and others offer good selected tubes.

    AMJBASS Supporting Member

    Jan 8, 2002
    Ontario, Canada
    An ECC83(12AX7) should last a very long time in your amp. Generally pre-amp tubes last longer than power tubes, and could quite possibly last the life of the amp. However, because it is in a Marshall, being a key part of the overdrive, depending on how hard you use it, it should last quite a while. When you begin to lose power, and it distorts early, you can just replace the tube with a 12AX7.
    ECC83 is the British name for 12AX7.
  12. rickbass

    rickbass Supporting Member

  13. What unbelievable response time! I owe you guys a beer. Thanks for the info. More later, I'm working right now. BTW, I'm not going to work this thing into the ground, I baby my amps. :rolleyes:

    Thanks again,
    Mike J.
  14. malibu

    malibu Guest

    Dec 26, 2001
    nice link rickbass -

    I was starting to post a reply with just the same info - that preamp tubes last alot longer than those of power amps.
    I run a pre-amp tube compressor (a Levelar into a Vox guitar amp) which someone said they changed to a Sovtek replacement 12AX7, and it improved the sound -- about $10 (or less) with some other tube brands of 12AX7 up much more to about $30.
  15. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    I own some 30-40 year old tube amps that still have the factory original preamp tubes in them.

    In hybrid tube/solid state designs like your amp, the tubes are not driven with as high a voltage as in all-tube amps which only increases life expectancy even further.
  16. Would I notice any difference if I replaced the original Mesa-Boogie 12AX7's in the Mesa pedal I have? I've heard their tubes are junky. What would be the difference if I got some newer, 'better' tubes? And what kind would those better tubes be anyway?
    Pbassmanca likes this.
  17. Steven Green

    Steven Green

    Jul 25, 2001
    Pacific NW
    I think Mesa uses Sovtek tubes for the V-Twin and there are better replacements. Also, it depends on the sound you're after...

    In my Aguilar DB 680 pre, it has 12AX7 & 7025 (I think), what's the different? I heard they are basically the same thing...
  18. Wow, I never thought they could possibly last that long. The only tube amp I ever owned was a Fender Bassman 100, which I bought from an old boss of mine 20 years ago. I put 4 new tubes in it and then sold it within six months, so I had no way of judging a tube's life.

    Anyway, I can't give a full report of how the Marshall sounds yet, but, just to give you guys a hint on some others:

    Fender Blues Jr. - Very nice old school Fender tube tone. Tried it back to back with a Princeton 65 - The Blues Jr. won. (Princeton didn't sound bad though)

    Tech 21 Trademark 10 - This is one versatile little devil. It's says it's got the circuitry of the Guitar Sansamp in it; whatever it has, it sounds real good.
    It's $299.00 at Sam Ash, I just checked M/F and it's $249.00 there. Always comparison shop.

    I played two Telecasters, one Strat and an Epiphone Sheraton II. (so nice)

    Thanks for the info, my mind is at ease.
    Mike J.
  19. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    ECC83 is European nomenclature for the 12AX7.

    7025 is a low noise version of the 12AX7.

    CV4004 is a Mullard version of the 7025 designed for military applications.

    5751 is a tube designed for use by the military. The internal construction is very solid and compact. 5751 tubes have 60% of the gain of a 12AX7. Highs are suposed to be subdued on the 5751.

    ECC83, 12AX7(A, WA, LPS) 7025, CV4004 are interchangable and all have the same gain spec.

    5751, 12AU7, 12AT7, ECC81 are interchangable with 12AX7 but have lower gain specs.

    Each of us has opinions in matters of tone. I've spent some time and money trying various tubes in my Demeter and SWR preamps. I prefer Telefunken smooth plate ECC83's in the Demeter and RCA long plate 7025's in the Grand Prix.

    I have yet to find a currently manufactured tube that comes close to the clarity and detail I get with Telefunken and RCA tubes. I've tried Sovetk, JJ, Chinese and EI. The older Groove Tubes 7025's (EI manufacture with dark grey plates) sound the best of the recently manufactured tubes that I've tried. The Sovtek 12AX7LPS also sounds quite nice but has the reputation of being prone to being microphonic.

    Many used and NOS tubes are sold on Ebay auctions and distributors sometimes find a stash and make them available. NOS Telefunken ECC83's go for around $100 and RCA 7025's go for about $50 when you can find a dealer that has them.

    Sounds expensive until you consider that the SWR Grand Prix is all but unusable IMO with the original Groove Tubes 12AX7 (made in China). The highs are harsh and the mids are gritty and nasal sounding. Plug in one of those $50 RCA 7025's and that $799 retail preamp is a new animal. Lows are deep and clear, mids have beautiful defination and round tone and the highs are sweet and smooth.

    In my bass preamps, I prefer the tone of tubes with long plate assemblies. The lows usually sound more detailed and clear and the highs lack the harshness of some short plate designs.

    Clearly YMMV. I love the tone of my bass rig and some of you certainly would not like it. Still, tubes are relatively inexpensive and worth experimenting with IMO. One source is WWW.thetubeshop.com

    Pbassmanca and globert like this.
  20. Michael - I too have a Marshall guitar amp


    **Looks around, nothing has been thrown**

    It's a Valvestate 8080 - about 7 years old. Quite quicky after getting it I followed a recommendation from a guy in a music store to swap the Marshall ECC83/12AX7 with a Sovtek High Gain number (can't remember the exact designation) The valve cost me £4 (about $6) I swapped it out (it's a doddle, just make sure the amp has been off overnight - the valve is cool and any residual charge is gone). The Sovtek saturates at a lower gain level, so gets fatter quicker, probably not that much fatter at full gain - but I've been too lazy to swap it back.

    So far, I've used it fairly well over the 7 years it's been gigged a few times (not often though) and I've always got the spare Marshall original. I think you'll find it lasts a good number of years!

Share This Page