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Dual Cabinets

Discussion in 'Amps [BG]' started by micahbell, Dec 6, 2012.

  1. micahbell

    micahbell

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    I have a mono power amp that I use for my bass rig, and I have always just used a single 410 cab.

    Last night I sold my 410, and ordered two Aguilar DB 112s, do I have a question about how to hook it up.

    My power amp has two outputs-one labeled "speaker" and the other "ext"

    Should I use both outputs, or use speaker and jump from one cab to the next? What difference does it make?

    Thanks
  2. skychief

    skychief Supporting Member

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    Either method is fine. They will both achieve a parallel connection to your cabs. Make sure the combined impedance of the new cabs do not exceed the minimum impedance of the power amp.
  3. RickenBoogie

    RickenBoogie

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    Yup, same thing either way. And yeah, make sure the combined load is not less than the amp's minimum.
  4. micahbell

    micahbell

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    Cool thanks.

    I know my amp can for sure handle 4 ohms, but the amp isn't labeled and it was a small production run from the late 60s so there is no documentation.

    Is there any way to find out how low I can safely run my amp?
  5. alembicbones

    alembicbones

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    Question for you all. What kind of configuration would be running the cabs in series?

    Bones
  6. skychief

    skychief Supporting Member

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    If you have no documentation, and theres no Z markings on the amp, how do you know it can handle 4 ohms?

    Do you mean it doesnt "give up the smoke" with a 4 ohm load? Im not trying to be cute, just trying to understand how you arrived at that conclusion.

    Anyway, let's assume it can handle a 4 ohm load. Then you'd want the 112's to be 8 ohm cabs.
  7. micahbell

    micahbell

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    I sent an email to an expert on the amps and he said it could run 4 ohms no problem, but he wasn't sure about 2 ohms.
  8. skychief

    skychief Supporting Member

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    Oh..OK,,. I wouldn't risk putting a 2 ohm load on a solid state amp designed for a 4 ohm load. That's begging for trouble.

    Your Aguilar cabs are 8 ohm, I hope.
  9. Downunderwonder

    Downunderwonder

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    An unusual one.

    You need special cabling or a go between box of special wired jacks. You wouldn't do it with a tube amp as one fault could fry it from open circuit.
  10. micahbell

    micahbell

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    Sorry, I forgot to say - it's a tube power amp. Does that make a difference?

    And yes - I ordered 8 ohm cabs
  11. skychief

    skychief Supporting Member

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    Thats a little trickier configuration, but entirely possible.

    One method involves making some wiring changes in the cabs and you cannot use the 2nd output jack of the amp.

    The downside to this configuration is once the wiring change has been made to the cab(s), they will only function in a series configuration; they can no longer be paired with a "normally" wired cab.

    There is another method (better, actually) which involves the use of a special box which does the wiring change for you,,, you have 1 spkr cable from the amp to the series box, and then 2 more spkr cables from the box to each cab.

    The only downside to this method I can think of is, you're tripping over a bunch of speaker cables. :atoz:
  12. jlepre

    jlepre Supporting Member

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    Do we KNOW if the cabs are 8 ohm? I hate to assume.
  13. jlepre

    jlepre Supporting Member

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    OK I feel better now. I would say your safe as long as you're POSITIVE the amp can handle a 4 ohm load.
  14. skychief

    skychief Supporting Member

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    Ummm yah, it kinda does. :D


    No worries, Youll be fine with the 8 ohm Aguilars.

    Most (but not all) tube amps can handle a 2 ohm load. Because of the output transformer the speaker drivers are electrically isolated the output stage of the amp. However with a solid-state amp, the speaker is actually part of it.

    Some tube amps have switchable impedance settings for the speaker(s) It matches the impedance of the speaker to the impedance of the secondary windings of the output transformer. This ensures the amp is running at peak efficiency and extends the life of the output tubes. In a low-power tube amp (under 50 watts) this is kinda important. With the bigger amps, not so critical.
  15. Downunderwonder

    Downunderwonder

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    What amp?

    Tube amps like to run on the nominal impedance load they were designed to run on. Most have multiple taps on the output transformer to run a selection of possible loads.

    There may be an internal jumper to swap between 8 and 4 ohms.
  16. micahbell

    micahbell

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    It's a Garnet BTO PA 200 watt power amp from about 69

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