How to test amplifier for maxiumum clean power

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. If you don't have an oscilloscope, hook up a speaker in series with a 100 ohm resistor as sown in the video.

Category:

Science & Technology

Tags:

• amp

[Alric96]

Nice video. Thank you. Where did you get the signal generator kit? What's the make and model info?

[vegmatic1966]

@Alric96, I bought it at parts express. It is the only function generator kit they stock.

[danpifs]

Excellent as always!

[orbiter8]

Thanks veg for this very informative & helpful video.

orb

[Iaintnosynystergates]

I have a Marshall amp head, and it goes 1X8 ohm 2X16 and 1X 16, but my Cab only goes 4 ohm and then 8 ohm stereo. What ohm rating shold i use? and will this damage my amp head? or the cab?

[ixfxi]

thanks for the video, great job

[CoupeDeville23]

What I dont understand is that after you reach the appropriate voltage, and then you go back to the deck and adjust the settings, it completely changes that voltage! If you go and turn the subwoofer control on the deck back up (test it at zero) afterwards, you'll be way over that target voltage. Are you supposed to leave the subwoofer setting to zero then?

[dvcsub]

im the second view cool.