Can I plug Blues Jr. Into my 4x12 cab?

Discussion in 'Amps and Cabs' started by zosozep7, Feb 22, 2009.

  1. zosozep7

    zosozep7 Gold Supporting Member

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    Hey all! I have a 4x12 cabinet left over from my B52 amp. Can I plug my Fender Blues Jr. into this cabinet? Will it sound ok?



    :munch
     
  2. zosozep7

    zosozep7 Gold Supporting Member

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    Thanks Jon!
     
  3. Billm

    Billm Member

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    The Blues Junior will also drive a 4 ohm load without problems.
     
  4. guitargeezer

    guitargeezer Silver Supporting Member

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    "Really? I always thought that amps could drive loads ABOVE their load without trouble, but not below.

    Am I wrong? Is it the other way around?"



    Trust me...or, rather, trust Billm. He is the most knowledgeable Blues Junior expert on the planet. Seriously.
     
  5. dk123123dk

    dk123123dk Member

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    I would stick with an 8 ohm speaker cab. You can risk it with a 4 ohm cab, or a 16 ohm cab if you want, but you would be stressing the transformer. Perhaps the transformer can handle the additional stress, but it can't be good for extended periods of time.

    dk
     
  6. blastastick

    blastastick Senior Member

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  7. strat56

    strat56 Member

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    I think I read or heard somewhere that with solid state amps it was ok to go with higher resistance but with tubes it was ok to go lower. I could be wrong though, it's happened before.
     
  8. Bottle_Rocket

    Bottle_Rocket Member

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    The lower the ohms of the cab the less resistance it offers. So an 8ohm amp run into 4 ohms will cause the amo to put out too much power for the amp to handle and may cause the tranny to blow up.
    On the other hand an 8 ohm amp run into a 16 ohm load will lower the power the amp puts out. You wont blow the transformer but may prematurely burn up your power tubes.
     
  9. GCDEF

    GCDEF Supporting Member

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    From the manual

    M . SPEAKER CONNECTOR - This jack provides a connection for the internal speaker OR any quality 8–ohm external speaker cabinet that you choose.

    The manual is pretty specific there. I'd believe it.
     
  10. Billm

    Billm Member

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    OK, let me explain.

    The output transformer's main job is to convert the impedance of the output tubes to the impedance of the speaker for maximum efficiency. When there's a mismatch, there's a reduction in efficiency. Most any tube amp can withstand a 100 percent mismatch, so an 8 ohm nominal rating can drive a 4 ohm load or a 16 without problems. One notable exception: don't try to go lower on amps with 2-ohm output.

    When the impedance gets too high on a tube amp, you get the possibility of flyback--arcs that can damage the output transformer or the output tubes. The BJr and many other modern amps have anti-flyback diodes in the output circuit to short out these high-voltage pulses.

    When the impedance gets too low, the tubes and output transformer run warm. But it takes a lot of current, like playing loud into a dead short, to damage either.

    Fender used the stock Blues Junior chassis in the Two Tone, a big cabinet with a 10 and a 12, both 8 ohm speakers, connected in parallel, a 4 ohm load.

    I drive a second 8 ohm cab all the time from my Blues Juniors. So do many of my customers.
     
  11. Trotter

    Trotter Supporting Member

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