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Cab ohm loads and Amp Ohm preferences

Discussion in 'Amps and Cabs [BG]' started by Myth_103, Jun 26, 2008.

  1. Jun 26, 2008 #1
    Myth_103

    Myth_103

    Jan 2, 2007
    Starkville, Mississippi
    Ok... So... What kind of an effect would a bass cab that's say.. 5.33 ohms or 2.7 ohms have on an all tube head that is specified to be used on either 2 or 4 ohms? What is the risk of damage there?
     
  2. Jun 26, 2008 #2
    jmac

    jmac

    May 23, 2007
    Lancaster, Pa
    A head that is rated at 2 ohms means that it can accept a load down to 2ohms. Do Not Go Below it. A Head has a certain power rating associated with the impedance spec. So if the Head is rated at 400Watts @ 2 Ohms and you connect a cabinet that is a higher impedance than 2 (like 4 or 8) then the Amp will output less power.

    In your case if the amp is rated at 2 ohms, then you can run either a 2.7 or 5.3 ohm cabinet. If the amp is rated at 4 ohms, then you would only connect the 5.3 ohm cabinet; not the 2.7 ohm cabinet.
     
  3. Jun 26, 2008 #3
    Myth_103

    Myth_103

    Jan 2, 2007
    Starkville, Mississippi
    So you're saying that as long as my amp ohm rating is set lower than the ohm rating of the cab it should be fine? Just don't go below the ohm load that the amp is set at? Am I understanding that correctly? That would be perfectly safe for both the cab AND the amp?
     
  4. Jun 26, 2008 #4
    projectMalamute

    projectMalamute

    Jan 9, 2008
    Westfield, MA, USA
    That response was not appropriate to an all tube amplifier. In fact, with a tube amp running too high of an impedance can be more damaging than too low.

    Use the setting closest to the load in question, if an amp is not robust enough to tolerate +/- a power of 2 then it is junk and just as well if it blows up. An old Ampeg would be fine, I have no idea about the VR.
     
  5. Jun 26, 2008 #5
    Bass_Pounder

    Bass_Pounder

    Jan 19, 2002
    Palm Coast, Florida
    No......

    What Jmac stated is only good for Solid State.

    Tube amps are completely different.

    Hopefully someone else can give you the right info (I really don't know much about tubes - I'm a S/S guy)
     
  6. Jun 26, 2008 #6
    JGR

    JGR The "G" is for Gustav Commercial User

    Jun 29, 2006
    Huntsville
    President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
    cab impedances aren't exact to begin with and a speaker's impedance varies anyway at different frequencies...

    anyway, 2.7 is close enough to 2 and 5.3 is close enough to 4. don't worry about it.

    JR