How To Tune An Amp With A Multimeter

(Last Updated On: March 15, 2024)

Superb audio systems make listening to music a joy. Yet, attaining such outstanding levels of quality isn’t only about owning good, functional audio equipment. Often, the problem could be found with the amplifier itself.

Having a properly tuned amplifier is crucial because tuning an amp can eliminate annoying background noise and irregular frequency response. Sometimes, the speakers may be unable to attain the desired volume.

Apart from improving sound quality, it reduces the risk of damaging speakers. This article discusses everything one needs to know about how to tune an amp with a multimeter.                                

Getting Ready

To get started, gather all the necessary tools. Luckily, tuning a car’s amp is possible without fancy or expensive tools. As the title suggests, the primary device is a multimeter, preferably a digital option.

This procedure also requires the following tools:

  • A speaker.
  • A calculator.
  • An audio source or CD (for test tone).
  • The amp’s manual.
  • A pen and jotter.

Read more: 5 Best Budget Multimeters Under $50 [2022 Review and Comparison]

How To Tune An Amp With A Multimeter

Adjusting the amp’s gain is an effective way to tune an amplifier. This method balances the output voltage of the head unit and amplifier’s input to avoid clipping and distortion. Below are the following steps to adjust an amp with a multimeter.

how to tune an amp with a multimeter
Have a better audio experience when driving with these steps.

Step 1: Disconnect every accessory from the amp

First, disconnect the car’s battery and carefully remove the car’s amplifier. Most vehicles have their amp under the hood, close to the windshield. If there is enough room to work, it may be unnecessary to remove the amplifier entirely.

Before starting the tuning process:

  • Disconnect all the accessories (including the speakers and subwoofers) from the amplifier.
  • Note the position of every connected cable before detaching cautiously.
  • Carefully remove the positive terminal to avoid damaging the amp, leaving the negative.  

Step 2: Switch the equalizer to zero

Observe the equalizer settings and switch everything to zero. Equalizer functions are basically to fine-tune sounds to make them more pleasant to the ears. Hence, leaving any of these settings enabled will affect the accuracy of the tuning procedure.

Step 3: Tune the gain to zero

Identify the gain knob or control and turn it to zero. The dial, in most amps, turns in an anti-clockwise direction to reduce the gain. If unsure of what to do, consult the manual for clarity. 

Step 4: Increase or reduce the volume to 75% of its maximum

Check the volume control, too, and ensure that the amplifier is at 75% of its total volume. Modifying the amp’s volume keeps distorted sounds from reaching the amp. However, the speaker must remain disconnected.

Step 5: Play a test sound

Play a test sound to tune the amplifier, preferably in a continuous loop. The ideal test sound must have a specific frequency – 60 Hz for subwoofer amplifiers, 1000 Hz for the mid-range amplifiers, and 2000 Hz for high-range ones. Whatever test sound you decide to use, the stereo must also have a sine-wave of 0 decibels. 

Step 6: Determine the speaker’s resistance with a multimeter

There is a need to test the resistance of the disconnected speaker to perfectly tune the amplifier. The multimeter is essential for this step. 

  • Plug the probes into the input jacks of the multimeter and turn its dial to the resistance (Ohms) setting.
  • Identify the loudspeaker’s terminals and connect the multimeter’s test leads according to their colors—the red (positive) test lead of the multimeter connected to the positive terminal and vice versa.
  • Write down the resistance value of the speaker. In many instances, the resistance values of loudspeakers are in a multiple of two. In other words, the resistance might be 2, 4, 8, or even 16 Ohms.

Therefore, pick a value in the multiple of two closest to the measurement displayed on the multimeter. For instance, if the meter shows 3.6 Ohms, the best option to go for is 4 ohms. 

Read more: 1-Ohm vs. 2-Ohm vs. 4-Ohm Subwoofer: Which Is The Best?

Step 7: Take note of the amplifier’s certified wattage output

The amplifier’s certified wattage output is essential in this procedure. Most times, this value is available in the manual of the amp. Check the manual to confirm and assess the wattage output with respect to the speaker’s resistance (Ohms). 

Step 8: Evaluate the ideal voltage for the amp

After determining the speaker’s resistance and amp’s output wattage, find the ideal voltage for the amplifier. One can evaluate this voltage using Ohm’s formula. The formula considers the resistance (R) and Wattage (P).

Voltage, V = √ (Wattage, P x Resistance, R)

Let’s have an example for a better understanding. Assume that the amplifier’s wattage, as obtained from the user manual, is 600 Watts, and the speaker’s resistance is 4 Ohms. Multiply the wattage by the resistance and find the square root to determine the voltage.

                                    Voltage = √ 600 Watts x 4 Ohms

                                    = 48.989 Volts or 49 Volts.

Therefore, the ideal voltage for gain control is 49 Volts. 

Step 9: Connect the multimeter with the amp

It is time to tune the amplifier. Plug the probes into the multimeter and set the dial to A.C voltage. Connect your amplifier’s speaker output to the multimeter’s test leads accordingly. 

Step 10: Modify the gain

With the multimeter connected to the amp, pay close attention to the voltage on the screen. Gradually adjust the gain’s knob till the multimeter reaches the calculated voltage (e.g., 49 Volts).

The gain is essentially the sensitivity of an amplifier. This setting ensures that the amp’s output is ideal for the speakers. Once the voltage is stable, the amp is now tuned. 

Step 11: Replicate for other amps

If there are other amplifiers in the vehicle’s sound system, this procedure should work effectively. Follow all the steps to achieve a better sound output. 

Step 12: Set the amp’s volume to zero

End the sound playing in the loop and turn down the amp’s volume to zero. Power off the stereo as well. 

Step 13: Plug all the accessories back in

Plug all the accessories back into the sound system. Connect the speakers, the power cables, amplifiers, and other things removed at the beginning of the tuning. Ensure that the arrangement of the wires is correct before powering it back on. 

Step 14: Now, listen to excellent music

Now you can listen to good music. Play a song and start enjoying your favorites from now on. 

Tune Your Amplifier With A Multimeter: Cheap And Easy Way.

Another Method To Tune An Amplifier

Besides the above procedure, there is another means to tune an amplifier, especially in the absence of a multimeter.

To do this, play some sounds (continuously) and listen carefully. Manually tune the bass boost and the gains of the amp till it feels more pleasant in the ears.

However, this method isn’t the best because the ears may be unable to pick up tiny distortions in the sound. 

Read more: How to install a car amplifier [with infographics]


There are other means to modify an amp – an oscilloscope and manual tuning with just the ears. Oscilloscopes are more efficient but expensive or challenging to use. The manual tuning method is the least effective.

A multimeter makes it easier for anyone, including those with basic knowledge of the device, to tune an amp with minimal stress. The procedure is suitable for any amplifier, even those multiple channels.

Furthermore, it is essential to note that various music genres have different tuning settings. Therefore, rather than switching the settings to a genre completely, finding a balance is more reasonable.

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