5 Power amplifiers

5.2 Output power

There's a lot of misinformation floating around about amplifier output power. While it's not as easy as a single amount of Watts, there's hardly any magic either. There are ways to use an amplifier, so there are ways to measure. Briefly:

  • Continuous or long term power: speaks for itself. Output power the amplifier can sustain for long periods of time.
  • Peak, burst or instantaneous power: power the amplifier can deliver in short bursts. Usually substantially higher than continuous power.
  • Music power: Popular term for peak power.
  • RMS power: There's no such thing as RMS power. It simply has no scientific meaning. What is usually meant by this specification is continuous power, though you really have to ask yourself if the specs can be trusted at all when this non-existing figure is listed.
  • Sine power: Another spec that has no scientific meaning, though usually refers to continuous power.
  • PMPO: Yet another spec that has no scientific meaning, and is used solely to blow up specs. Don't trust this. Sometimes referred to as "Preposterous Marketing Power Output"

The most important power rating for bass guitar is peak power. Musical instrument signals contain very high peaks and have moderate continuous power. In between the peaks, during times of reduced power levels, the amplifier circuitry can prepare itself for the next peak.

© Joris van den Heuvel 2001-2009