Current vs Watts for amps

April 22, 2021
 by Paul McGowan

8 comments on “Current vs Watts for amps”

  1. Some follow-up questions come to mind. Which approach provides the most pleasing sonic qualities, a speaker that presents a complex load matched to an amp that can provide a high current or a speaker that presents a simple load to an amp that does not? Does it depend on the type of music to which you listen? Or should you not generalize?

    1. Good afternoon MikeK!
      The kind of music you listen to on your system doesn’t matter at all.
      It’s just only your frenclicy response curves around the currant and voltage that your amp is producing.
      But if you have a speaker that gives your amp a tuff load to drive, then all depending on the amp, that’s gonna predict what the sound is gonna sound like.

  2. What role does short-circuit or over-current protection play? An amplifier without protection could easily be damaged by an accidental short circuit. In an amplifier with protection, a low impedance load could trigger the protection circuits because the load looks too much like a short circuit. If the protection is triggered, the amplifier is going to sound terrible. This may explain why some speakers have the reputation of being difficult to drive.

    1. Mark Thomas,
      You say (typed) that, “If the protection is triggered, the amplifier is going to sound terrible.”
      When in fact if the protection is triggered then the amplifier wont make a sound…nothing, nada, nichts, zilch, zero sound will come out of the amplifier.
      That’s the whole point of protection.

      1. If the protection works by disconnecting the load (the speakers) then I agree that the result will be silence. That’s quite annoying if it occurs in a fortissimo section when you have your “difficult to drive” speakers connected.

        I was actually thinking about the Safe Operation Area (SOA) protection that is often included in Class AB power amplifiers. This detects the condition where output transistors are delivering a high current into a low impedance load, and clamps the drive to the output stage. It normally involves just two additional transistors. SOA protection can be extremely effective as a way to avoid permanent damage when the output of an amplifier is shorted to ground. The SOA protection is supposed to allow the amplifier to deliver maximum power into any reasonable load. I was asking if the onset of this form of protection can produce audible distortion when load impedance is very low.

  3. I may be a blind Audiophile, but I do know a grate deal about this kind of a thing, when it comes to tube amps.
    For speakers like those that are made by Magnapan, a tube amp that has enough power can drive those without any problems.
    I haven’t had to try a pare of Magnapan speakers yet.
    But I’m quite sure that my Jolida JD-1000P all tube power amp wouldn’t have a problem driving them at all.
    All you really need for speakers like those, is an amp that can handle a 4 ohm load.
    Sure there are 4 ohm and 8 ohm taps on the back of my amp, but it can go all the way down to a 1.5 ohm load without braking a sweat.
    After all, it’s rated at 150 watts per channel.

  4. I recently bought a used pair of Quad ESL-63s. I drove them with my PrimaLuna Prologue integrated — great for my B&W 804Ss, sorry Paul! — and the results were “meh.” I then picked up a used Quad 44/405-2 combo on Audiogon and — HOLY CRAP! — the Quads came alive. I guess all that “current dumping” and “high current” advertising is true…

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