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  • M3 AO-29 Heaters

    In the AO-29, the heater wiring from the transformer runs to the first 6V6 and continues in a parallel path to the remaining tubes except for V10 (6BA6) bass preamp. One side of the 6BA6 heater is connected to the first 6V6 with 2 10 ohm resistors in parallel while the other side uses a wire. The question is why and would running the amp without the 6BA6 cause any problems?
    I went through the 6BA6 data sheets and other forums and didn't come up with an explanation. The only thing I could think of was these resistors serve to limit the heater current to the 6BA6.

  • #2
    Hello

    This tube 6BA6 = 5749
    Click image for larger version

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    Reducing voltage heater from 6 to 4V5 is a trick to increase reliability.

    JP

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    • #3
      Thanks JP - I've always been the curious type.

      Last Friday I was listening to a 4 piece blues band (guitar, bass, organ (M3) and drums). The KB player was talking about adding a wah pedal and I thought: M3 with no pedals - remove the pedal preamp and add an effects loop. Replace tube socket with a 9 pin shielded and there should be plenty of room with the pedal circuitry removed.


      Jim

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