Power amp + Guitar Cab

Discussion in 'Guitars' started by recordometer, Jan 24, 2006.

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  1. recordometer

    recordometer Guest

    Hi all,

    I've got a stereo power amp which is 250w per channel RMS at 4ohm;planning on using it after a guitar preamp in the signal chain

    I've also got a 4 x 12 400w guitar cab; it's wired so there's two inputs, one 8 ohm input for the left two speakers (200w), and one 8 ohm input for the right input, of the same power.

    Just wondering the best way to hook it up for maximum power output- is it possible to sort of bridge the two outputs of the power amp (it doesn't say anything about bridging in the manual), then run it into the guitar cab which i would have wired the two sides L + R in parallel?

    hope i'mb being clear enough

  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Feb 23, 2005
    You can simply run each of the (2) channels of the power amp to each "side" of the cab. This will provide an 8-ohm load to each side of the amp.No problem, this will simply not deliver the maximum available power from the amp...probably 150-175 watts instead of the 250/side.
    Leave it there. If you parallel ("daisey-chain") the 2 halves of the speaker cab together, you will end up with a 4-ohm mono load, and that is too low for a typical mono-bridged stereo power amp to "see". This represents a 2-ohm/channel load on the amp, and that can very easily cause a thermal condition on the amp, making it unstable and shut down.
    If you want to get the max from the amp, you should get another cab like the 1 you have now and use the 2 cabs on the 2 channels of the stereo amp.
  3. MilesAway

    MilesAway Guest

    why in the name of all that is good and true would you possibly want that much power for a guitar amp?
  4. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Feb 23, 2005
    12 watts from a cathode-biased pair of 6V6s makes me giddy with glee, but, hey, to each his own.
  5. cfaalm

    cfaalm Active Member

    Feb 21, 2005
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    More power to you

    What preamp are you using? Any FX? Is that a valve poweramp?

    That's a lot of watts there.

    If your amp's manual doesn't say anything about bridging, don't go there!

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