Can you swap a 12au7 for a 12ax7?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by NOVA70, Mar 21, 2005.


  1. NOVA70

    NOVA70 Supporting Member

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    Hi,
    Can anyone tell me if it OK to swap a 12au7 for a 12ax7 and if so what would be the results?
    Regards,
    Pat
     
  2. Blue Strat

    Blue Strat Member

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    You can but the considerably lower gain of the 12AU7 often makes this tube useless in guitar amps. The one exception is in high gain amps which have way too much gain and overdrive.
     
  3. WailinGuy

    WailinGuy Member

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    In a given circuit, a 12AU7 will usually draw significantly more idle current than a 12AX7. This might cause problems in certain modern PCB-based amps that have 1/4-watt plate resistors, instead of the usual 1/2-watt or 1-watt plate resistors found in vintage and boutique amps. There's the risk that the extra current draw may cause the power dissipated by the resistor to exceed its 1/4-watt rating and burn out.
     
  4. NOVA70

    NOVA70 Supporting Member

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    Thanks to all for the info.
    Regards,
    Pat
     

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