oh my Ohms are tired

Discussion in 'Amps [BG]' started by muddpuddle, Dec 22, 2013.

  1. muddpuddle


    Mar 5, 2012
    Can anybody help me understand amps and ohms

    I have an old peavy head that's rated 210 amps at 2 ohms. What would be the result of playing through a single 8 ohm speaker
  2. B-string

    B-string Gold Supporting Member

    I'm sure you meant 210 WATTS not amps. Being a SS amp, use of an 8 ohm speaker would just mean it will produce much less wattage from the amp.

    The "Stickies" are chocked full of ohms/wattage info.
  3. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Oh my is right! That would be 88,200 watts. I figure that you'd probably blow your speaker.

    First step in answering your question is to know what model amp you have.
  4. swamp_bass

    swamp_bass I love it when a groove comes together

    Nov 20, 2013
    North Cackalacky
    The general rule is that an amp's output will be half at double the speaker impedance. Many amps aren't quite linear that way, but it's a good general way to approximate.

    So 210 Watts into 2 ohms becomes:
    * 105 Watts into 4 ohms,
    * 60 Watts into 8 ohms.

    Many amps deviate from that general rule. Often amps that are "stable to 2 ohms" use active current limiting at 2 ohms that limits power to approximately the same output as 4 ohms. If that's the case, then your output into 8 ohms would be more like 100 watts.

    So somewhere between 50 and 100 is the ballpark.
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  6. That series of Peavey power amps is rated:

    210 watts into 2 ohms at 1% THD
    140 watts into 4 ohms
    80 watts into 8 ohms