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amps / ohms

Discussion in 'Amps and Cabs [BG]' started by lpbassics, Apr 8, 2002.


  1. lpbassics

    lpbassics Guest

    Jan 26, 2002
    WI
    now this question is totally theoretical (so don't be like: why would you do this anyway?)

    I'm just wondering lets say you have an amp that is rated down to ohhhhhhh 4 ohms. And you are using it with a cab that is 2 ohms.

    I understand this is a bad thing, but how does this damage the amp (other than just it overheats, i'm looking specific, so i know)? If you played at low volumes would it still damage the amp? Does anything happen to the cab?

    thx, just tryin to learn

    lp
     
  2. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    It could damage the amp. If you're lucky and have an amp with good protection circuitry built in, it'll just make it shut down or current-limit to protect itself. That'll still interrupt your playing, but at least you'll be able to use it again.

    An amp's load impedance spec is a MINIMUM limit; the speaker load you hook up to it should be equal to or higher than that figure.
     
  3. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    I'm not an expert, so please someone correct me if I'm wrong but I try to explain in simple words (excuse my english please):

    A (solid state) amp puts out a certain voltage. This results in the flow of a certain current depending on the impedance of the cab. If the impedance is low, the current is high.
    If the impedance is too low for the specific amp (e.g. 2Ohms instead of 4) this will result in a current which is too high for the amp to handle it safely (because the parts are not designed for this).

    Rest of story: see Bob's post.

    Matthias
     
  4. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Matthias said it very well.

    The only thing I'd clarify is that a solid-state amp puts out a voltage that is for the most part directly proportional to the input signal voltage. That might seem obvious to most, but not everyone knows that, or they may have been told by a misinformed salesman that an amp always puts out a voltage.
     
  5. lpbassics

    lpbassics Guest

    Jan 26, 2002
    WI
    thx all

    but would you still damage the amp even running it at very low levels?

    lp
     
  6. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    No, that's not likely. But you also don't need a 2-ohm cabinet if you're going to be running at very low levels, either.
     
  7. lpbassics

    lpbassics Guest

    Jan 26, 2002
    WI
    hey theoretical question...

    but thx a lot everyone!

    lp
     
  8. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    Yes I should have stated that in a basic explanation like this (but for me this goes without saying)

    Matthias