What are the risks? 6G6 Bassman head into 16ohm Marshall cab

Discussion in 'Amps and Cabs' started by m@2, Sep 10, 2008.

  1. m@2

    m@2 Member

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    Hi TGP,
    Aside from volume or tone impacts, what actual risks are there to running a 6g6 Bassman head (4 ohm output) into a Marshall 4X12 cab (16ohms). Is the potential risk to the speakers, tubes, or the transformers, or both... I have seen many people power marshall 4X12's with bassman, but I don't want to F up my 6G6. I have run the bassman into 8ohm cabs many times. These old bassman seem pretty bullet proof, but I don't want to destroy my amp

    Second question... Is it more risky to run a 16ohm amp into a 4ohm cab?

    Any insight would be much appreciated.
     
  2. FrankieSixxxgun

    FrankieSixxxgun Member

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    A higher impedance cab than the amp will cause the power tubes to flash voltage at the OT. I wouldn't do it, especially with a nice amp like a Bassman. If you rewire that Marshall cab as it has 4x16 ohm speakers, you can make it 4 ohms though. Now you know the easy way that people run a Bassman into a Marshall cab safely. :D

    Edit - Your second question, I totally forgot it. Running a lower impedance speaker into a higher impedance amp will tax the power tubes pretty heavily. Generally this is technically, "Safer," since it'll likely just blow out a set of power tubes, but I wouldn't go nuts with it. I run an impedance mismatch like that with my amp since I'm running 6V6s in my JCM 800, which sets the impedance way off, and I run the amp pretty hard. No issues yet, but JJs are pretty rugged power tubes.
     
  3. m@2

    m@2 Member

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    yah, i was hoping to avoid a rewire because it would be a borrowed cab, and he uses a 16ohm marshall head. Thanks for the input : )
     
  4. FrankieSixxxgun

    FrankieSixxxgun Member

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    Tell him to stop being a nancy boy and set his tap to 4 ohms. If it's a newer Marshall cab you can flip the switch in the back. My 425A and B have a 16 ohm jack, a 4 ohm jack, and if I flip the switch two stereo 8 ohm jacks. Kinda overkill, but I guess it's convenient for some.
     
  5. BluesForDan

    BluesForDan Member

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    Mismatching is not advisable. Although a 2 to 1 ratio can be tolerated by some gear, it really should be only for an emergency basis (all that you have on hand at a gig after your primary amp blew up). A 4 to 1 ratio is just begging for more magic smoke to leave the circuit forever, never to be put back again. Tubes are easily replaced, transformers are not because they are so integral to the originality of the amp.

    The damage is mostly for the amp, but I'm not discounting possibility of speaker damage, too.

    Matched gear blows up enough as it is, why take the chance of increasing the odds with mismatched?

    Rewire your 16 ohm cab to 4 ohms, or get another cab.
     
  6. Griz

    Griz Member

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    I have a '69-70 4x12 with original Greenbacks, wired to switch between 4 and 16 ohms. Works great with my '62 Bassman.
     

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