What's the pre-amp tube lay-out for a '66 Bassman?

Discussion in 'Amp Tech Center' started by surlydude, May 3, 2019.

  1. surlydude

    surlydude TDPRI Member

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    Aside from the 6L6s and the PI next to it, what are the functions of the other 12ax7s, starting from V1? Thanks.
     
  2. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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  3. Obelisk

    Obelisk Tele-Afflicted

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    I am not a tech, but the first preamp tube would be for the bass instrument channel input and tonestack. V2 would be the second gain stage for the bass channel. I don't believe it is a cathode follower like the original 5F6A Bassman. Only one triode is used of V2. V3 would be the normal input channel and tonestack. Here is a link with a more thorough explanation though surely others will chime in.

    http://fenderguru.com/amps/bassman/
     
  4. Ten Over

    Ten Over Tele-Holic

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    V1A and V1B are the Bass Instrument channel with the tone stack in between. V3A and V3B are the Normal channel with the tone stack in between. V2B is the lone 7025 shown in the schematics. It is wired-up differently from model to model during that era, but it always seems to be V2B. V2A is not used. V4A and V4B are the PI.
     
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  5. surlydude

    surlydude TDPRI Member

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    Thanks, guys!
     
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