How to Set Amp Gain With a Multimeter

If you have an amplifier, you probably want to get the most performance possible out of it. Setting the gain on the amp is an important step to achieve that, as well as to protect your equipment.

What is Multimeter ?

Multimeters are the perfect tool for electrical diagnostics. They help you test and measure everything from simple voltages to complex faults in your home wiring. Analog multimeters have a needle that moves across a scale, while digital multimeters show values on a screen. Regardless of which type of multimeter you use, they’re both useful for everything from measuring battery voltage to detecting wiring problems in your home’s electrical system.


Multimeter is a tool for electricians. They use it to troubleshoot electrical problems. It’s used on motors, appliances, circuits, power supplies, and wiring systems.

Testing the output levels of an amplifier with a multimeter and a little math ensures it’s set to the correct gain for your stereo. To start, match the amp’s input level with the stereo’s output level. Then use your multimeter to measure the AC voltage of the amp’s high-voltage output. Then use a little math to figure out what setting on the amplifier provides the correct gain for your system.


  1. Use a multimeter to measure the resistance of the speaker. Place one probe on the positive lead and the other probe on the negative lead. Note the resistance..
  2. To find the right amp, check the manual. It will show you the output wattage and ohms at your speaker’s resistance.
  3. Calculate the AC voltage output for the amplifier. This equation can be solved as: voltage equals the square root of wattage times resistance. Use the formula power = voltage x resistance to solve for the desired AC voltage output of your amplifier. Then find the square root of this number to determine your amplifier’s RMS voltage output.
  4. Shut off the power to the amplifier. Then, remove the wires from all speakers and subwoofers, and leave the amplifier connected to a power source.
  5. Set the music to a medium-high volume.
  6. Connect the multimeter to the amplifier. Put the positive probe in the positive terminal and the negative probe in the negative terminal.
  7. Listen to a 60 Hz test tone CD on your stereo system.


First, you’ll need to connect the multimeter to the amplifier. Next, you’ll adjust the amplifier’s gain knob until the multimeter reads the desired AC output voltage reading (which you found through the math equation). Now that the amplifier’s gain is correctly set, you’re done!

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