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Power amp + Guitar Cab

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

  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 Moderator

    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 Moderator

    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
    Home Page:
    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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