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V4B-H true power output @4ohms

Discussion in 'Amps and Cabs [BG]' started by rumblefish, Dec 22, 2003.

  1. all hail the V4-B and its' modern day decendant, the V4B-H...Ampeg's ONLY head with a secret sound-shaping button on the back panel named after a Led Zeppelin Album...( Presence )

    My question:
    The V4B-H is rated at 100 watts maximum power output at 8 ohms.
    But it's also rated at 100 watts power output
    with a 4-ohm loan.
    Why doesn't the 4-ohm rating jump up like most other amps?
    Any guesstimate on the actual 4-ohm output with this 2/3's of a SVT head?
    I believe Ampeg is being conservative with its' ratings.
  2. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    No, Ampeg is being honest. The V4B puts out 100 watts which is 1/3 of the SVT's output.

    Tube amps put out the same power into different loads because of how they are designed. Solid state amps vary their output according to the load they are matched with.

    The V4B will put out 100W safely into the loads you select using the impedance switch. I suppose you could try to coax more by mismatching impedances on purpose but chances are you'll fry the amp before the first song is done.
  3. bassmanjones


    Feb 23, 2002
    Boston, MA
    I actually asked this question to Aguilar when I was looking into their tube amp and the answer they gave me is that tube amps (unlike solid state amps) put out the exact same wattage at different ohm loads. So, a 100 watt tube amp at 16 ohms is a 100 watt tube amp at 4 ohms.

    BUT, they warned me that you only match the impedence of the cab to what the amp is rated for and never differently. So, for example, you can put an 8 ohm tube amp with an 8 ohm cabinet but not a 2 ohm cabinet load, etc.

    I don't have the explanation why the wattage never changes or why you have to match up the resistance (but I'm sure someone here does), but I trust what they say to be true.
  4. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    It's because tube amps have an output transformer.