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YBA200 Tube questions

Discussion in 'Amps and Cabs [BG]' started by protoz, Jan 12, 2006.

  1. protoz


    Nov 30, 2000
    I'm looking at picking up a YBA200 at the end of the month and I had some questions after checking out all the tube swap threads.

    The preamp section has 2 12AX7s and 1 12AU7 as a splitter. Can I put a higher gain tube in the splitter? If so how will that change the tone? (thinking 12AT7 or an AY)

    Changing the power tubes to KT88s added some power and headroom to the amp which would be nice to have. What adjustments would I need to make to get them to work nicely? It's a fixed bias with an 'auto-biasing technology' so I'm thinking a mod would be needed to get it to work.

    Thanks in advance
  2. Higher gain tubes in the inverter will DECREASE your amount of usable power, how much depends on the their plate current capability. It'll be like sticking an overdrive pedal in your signal chain all the time. If you like headroom this is exactly the opposite of the way you want to go.

    A KT88 and 6550 bias so similarly that no mods should be needed.
  3. protoz


    Nov 30, 2000
    Alright thanks for the heads up on that. Especially the inverter tube before I went and tossed a 12AX7 in there and cried.
  4. denton57

    denton57 Supporting Member

    Nov 1, 2005
    I've been messing around with mine. I replaced the original preamp with NOS 12at7's, and it lost too much overall usable volume for me. Then I put in some Ruby 12ax7's in. Now I'm getting ready to order a complete JJ/Tesla retube kit today or tomorrow with the Kt 88's. Should we get a rebias for the power tubes? Anyone? Im hoping that a Ric 4003 into a Kt88'd Yba into an Ampeg 8x10 will be enough :bassist:
  5. You don't need to rebias the amp, it will run about 4V colder than the optimum for the KT88s, but I have had no problems with mine.

    I am going tpo try the JJ 803 (long plate 12ax7) in the preamp next too see what kind of tone that gets me.