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Replacement tubes for a Mesa Boogie Walkabout

Discussion in 'Amps and Cabs [BG]' started by Guapo, Jul 28, 2005.

  1. I've just bought a second hand Walkabout amp about 3-4 y.o. and I would like to replace the original 12AX7 tubes. I've read that the original Mesa Boogie 12AX7 tubes (Sovtek made) should have some level of microphonics. Any suggestion for good replcement tubes for this particular amp? I play upright bass, often with slap.
  2. eldave777


    May 24, 2005
    Boogie tubes are usually less expensive than sovtek. Also boogie puts a 6 month guarantee on tubes. They also sell them in matched pairs and they say your amp won't need to be biased if you stick with boogie tubes.
  3. BillisCool


    Apr 16, 2005
    Buffalo, NY
    Preamp tubes NEVER need to biased.

    Read the reviews, pick the ones you think might suit you best.

    I use JJ's and they sound excellent.
  4. Thanks guys. I have one more question. Do the 12AX7 have to be of the same brand? As far as I can read, they serve different purposes in the circuitry of the Walkabout. Am I wrong in saying that the one in the preamp will mostly affect the final sound?
  5. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    The short answer is that the JJ's really are an excellent choice, and my favorite option for the Walkabout among the tubes currently in production. The longer answer can be read on my blog, but here's the relevant information for the Walkabout:

  6. Thanks a lot for the detailed review of the tubes! Upon that I have chosen 4 different tubes and I'm going to test them as soon as I receive them. One last question: is the preamp tube the one on the right (facing the front of the Walkabout) close to the air grille?
  7. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    The preamp tube is the one closest to the front panel, and the driver tube is the one closer to the middle of the amp.

  8. Tom, would you go for two identical tubes or would you also consider a mix. I've read somewhere that one should choose one tube for the preamp section to achieve a particular tone and temper, while the mosfet driver tube should be more neutral. Do you agree on this?
  9. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    I don't think that there is any need to use two identical tubes, unless those happen to be the two tubes that sound the best in their respective positions. The two tubes have different jobs to do, and therefore, it's entirely possible (if not likely) that two different types of tubes would sound the best.
  10. just ordered a bunch of tubes from "Doug's Tubes," great guy, very helpful! :bassist:
  11. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    Cool! Let us know how your experiments work out!

  12. ok now I also did some tests with a bunch of tubes, some of them new, some other vintage tubes.
    It hasn't been easy and still don't think I'm done with it, as there are so many different combinations of the the preamp tube and the mosfet driver tube.

    The tubes I have tested are:

    Groove 12AX7M (Mullard) new
    JJ Tesla 12aAX7 new
    TungSol 12AX7 new
    Sovtek 12AX7LPS new
    Electro Harmonix 12AX7
    Telefunken ECC83 vintage
    Mullard CV4004 vintage
    Mullard ECC83 yellow label vintage

    The best combination I got so far is the Mullard CV4004 with a JJ Tesla 12aAX7 in the mosfet driver slot. The CV4004 wasn't as boomy and aggressive on the lows as the Mullard ECC83, yet very clear and defined and with a massive bass. The Telefunken was perhaps the best on mids and mid-lows, but the highs were a bit too mellow for my taste.

    The vintage tubes didn't come cheap. The best of the new tubes for the preamp slot would have been the Groove 12AX7M, which was close to the Mullards. Unfortunately it also produced a tic-tac sound that added an unwanted, fixed pace metronome function to the Walkabout. It must have been a bad tube.
  13. JOME77

    JOME77 Supporting Member

    Aug 18, 2002
    Glad I came upon this thread! I read a similar thread several months ago and actually printed out Tom's summary of various tubes and their sound tendencies. I planned on ordering a few to experiment with but just never got around to it. I think I'll do that now. I do have to say though that even with the stock tubes in my Walkabout I've been absolutely amazed with the sounds that I've gotten. And the fact the Mesa put it all in a 13 lb package is amazing! My Thunderfunk TFB-420 is still my main amp but I'll always keep the Mesa around for the rock gigs! Such a huge warm sound! :bassist:
  14. Joe, the Walkabout can sound better with other tubes but the standard Mesa ones, which I believe are some sort of Sovtek. Russian preamp tubes generally are not bad, but it seems like they weight more gain than sound quality. I find the sound of the standard valves a bit muddy and unfocused. If you like a massive deep bass then get a Mullard or even the Groove replica - hopefully these 12AX7M are not all of them bad, as mine was. If you like a more sober, cultivated and complex sound with many details, the Telefunken would probably be the one for you.

    When I started reading about preamp tubes I just could not believe that a 40 years old tube could sound better than a modern one ... but I realized, it's actually true.