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Tube replacement for Genz Benz 9.2

Discussion in 'Amps and Cabs [BG]' started by Dig You, Oct 28, 2018.


  1. Dig You

    Dig You

    Jul 15, 2012
    Littleton, NH
    I'm looking for recommendations for a tube replacement for the 12AX7 in the GB Shuttle 9.2. My aim is for something clean and fast, retaining the fatness of the factory tube.
    Any help would be appreciated.

    Thank you.
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The tube in your amp was selected for the best balance between overall performance, low noise/microphonics and long life (85% should last over 20 years and still meet design spec, I would expect over 50 will last 30 years or more). There are also circuit elements that normalize the wide variation in parameters due to manufacturing tolerances so that most tubes will sound very similarly, that way everybody gets a good sounding amp and nobody gets stuck with a dog. It's all about consistency.

    There were 2 different tubes that consistently met this criteria when your amp was built, they are the Ruby 12AX7-AC5 and the JJ ECC-83.

    Something I am seeing on amps that come in for service is damage due to careless or rough handling when changing tubes. Bent pins or pins not aligned and forced into the socket can damage the socket. I recommend leaving well enough alone. If it ain't broke, don't fix it ;)
     
    wave rider and Dig You like this.
  3. Dig You

    Dig You

    Jul 15, 2012
    Littleton, NH
    Thanks very much for responding.... so the reason for considering the tube change is that the amp seems a bit dirtier than it used to. It gets a bit nasty when I lean into it and it didn't previously. I've done my due diligence with signal path, testing different cabs etc.... but still a bit grungy. I'd like to know if you favor one replacement tube over another. Thanks again for weighing in.
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Either of the two tubes I mentioned will work fine, I perhaps prefer the JJ, but the differences are tiny.

    Be gentle when replacing the tube, the retainer should just touch the tube and not push so hard on it that it bends the socket PCB. No air wrenches needed ;)
     
    Dig You likes this.
  5. Dig You

    Dig You

    Jul 15, 2012
    Littleton, NH
    Thanks aged horse..... JJ is inbound as I type.
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Don't get your hope up too much though, it's unlikely the cause of any problem.
     

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