Testing for maximum clean sine wave output power from audio power amplifier. Q. Can I hurt my amp in doing this? A. If you have everything hooked up properly, no. Due to the dubious quality of some products today, there is some chance that the amplifier could be damaged. Perform at your own risk. Q. Why can’t I use a speaker instead of a resistor in the test? A. The impedance rating of a speaker is a nominal value. It will vary at different frequencies due to such factors as resonance (among others). A non inductive resistor must be used. Q. What is the formula to find power? A. It is the RMS output voltage squared divided by the impedance. Impedance being the resistance of the load resistor used. Vrms^2 / R = Wout (rms) Q. What does RMS mean? A. Root mean squared. Without getting technical it simply means the real usable power delivered into a load. An amplifier should be rated with a rms value and not the peak output power nonsense that some manufacturers use. “big numbers entice small minds”. Don’t be small minded! Tips: The resistor impedance should NOT be less than what the amp is rated for. For example, if the amplifier is rated for 8 Ohms minimum, never test with a 4 Ohm resistance or the amp could be damaged due to the excessive current. Set input level to minimum before powering up the amp. Turn up the level to clipping level and back off slightly until smooth sine wave is seen or harshness is gone. Be sure to unhook any speakers before hooking up the resistor …
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