Impedance and anp damage question

Discussion in 'Amps and Cabs' started by Jd_mercer, Apr 25, 2016.

  1. Jd_mercer

    Jd_mercer Member

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    Hello everyone!
    First post here. I have an egnater 15w tweaker tube head that has the three impedance switch and a 12 inch speaker which is 8 ohms. Today, for a little over an hour I jammed with my band not realizing that my amp was switched to the 4 ohm impedance, going into a 8 ohm load. I must have nudged the switch when I was carrying the head. I didn't notice anything happening differently, granted I didn't know to look for anything. My question is this:
    Would I be able to tell if my amp got damaged? Like smoke or something indicating a problem. Or is this going to sneak up on me??
    When I got home I plugged it in, the right way..., and nothing seemed different, even though I didn't crank it as loud.

    Really appreciate the input. Thanks in advanced!
     
    Last edited: Apr 25, 2016
  2. Drockafella80

    Drockafella80 Supporting Member

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    A 4ohm amp into an 8ohm cab is fine.. It's an 8ohm amp into a 4ohm cab that would be an issue. All you did was cut down on volume and dynamics, but your amp is fine.
     
  3. kimock

    kimock Member

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    You're fine. I wouldn't make a habit of it, try to keep it matched, but it's not likely you'll damage anything with so brief a mismatch.
     
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  4. Jd_mercer

    Jd_mercer Member

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  5. DrainBamage

    DrainBamage Member

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    You can mismatch up or down. It cuts power and the frequency changes. The recommended ohm setting is for max output, that's it.
     
  6. GCDEF

    GCDEF Supporting Member

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    Wow. If your amp still works, it's fine, but no, it's not guaranteed that you can mismatch up or down. Most amps can tolerate it, but it's better to avoid it as the possibility of damage is real. With tube amps, you're better running into too low a load than too high. Solid state is the other way around.
     
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  7. IM4Tone

    IM4Tone Member

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    Nope, that's backwards for a tube amp, correct for a ss amp as the following post states.
    This is commonly felt to be true for tube amps w/ a sufficiently robust OT, but I avoid the practice.

    It's unlikely you've harmed the amp since it sounds the same now.
     
    zenas likes this.
  8. MHG

    MHG Member

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    8ohms into a 16 ohm cab is fine. Many people do this on purpose to coax a different tone and feel out of their amps. When I purchased a Sommatone amp, I was told to mismatch in order to achieve earlier, and smoother, breakup. Sounded fantastic. Never go 8 into 4, or 16 into 8 though!
     
  9. GCDEF

    GCDEF Supporting Member

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    Please stop, or at least do some research first.
     
  10. MHG

    MHG Member

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    This is what I've been told by many reputable builders over the years. I've never had a problem going 8 ohms into a 16 ohm cab.
     
    Last edited: Apr 26, 2016
  11. DrainBamage

    DrainBamage Member

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    Well who are folks going to agree with? The gear page "internet techs" or example a man whos been in the business since the 70s and wrote multiple books on power supply? All it takes is one person in one thread and everyone thinks it bad for the amp!
     
  12. VaughnC

    VaughnC Supporting Member

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    Tube amps typically don't like the load impedance to be too high in relation to the amp impedance setting due to the flyback voltage it can generate. As a matter of fact, many amp builders use shorting type speaker jacks to prevent flyback from occurring in the event you forget to plug in a speaker cable...and this is a dead short on the output transformer.

    However, one impedence step is usually not enough of a difference to cause a problem with flyback. So, while I might feel ok running a 4 ohm amp into an 8 ohm speaker, I'd be a little nervous using the same 4 ohm amp into a 16 ohm speaker. But, then again, not all output transformers are created equal and some may have better insulation than others to somewhat tolerate flyback.
     
    IM4Tone likes this.

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