How to Tune an Amplifier With a Multimeter: Easiest Methods

If you’ve recently ridden in a high-end car, you might have experienced the joy of hearing music blaring out of the speakers. Car stereos are the norm in a vast majority of vehicles.

Years ago, these gadgets were only available to the uber-rich or new car owners with a few bucks to spare. But how do these amplifiers produce sound? Can they be altered for better audio output?

It’s possible to tune an amp with a multimeter, and the key is knowing how to gain adjustment control. This skill is helpful if you’re looking to get the best sound experience out of a car system. Aside from improving the quality of your music, tuning your amplifier also increases its shelf-life.

Before learning how to tune an amplifier with a multimeter, you need to understand what an amp and multimeter are.

What Is an Amp?

An amplifier is a device that essentially magnifies a signal, be it its power, current, or voltage. Although these devices have multiple uses, they are mainly used in music equipment and many electronic devices.

What Is a Multimeter?

A multimeter is used to testelectrical or electronic devices’ electrical properties. Multimeters are helpful because you can test multiple factors such as frequency, voltage, resistance, and currency all in one go. Some sophisticated multimeters also perform diode, temperature, and continuity tests.

Your multimeter will have a large knob, and all you need to do is connect its testing probes and adjust the knob for the correct reading.

How to Tune an Amplifier With a Multimeter: 10 Easy Steps

Before you begin, gather all the tools required for this job. These include:

Connect the Multimeter to the Amp

Switch off the car, disconnect the speakers from the main power supply, and locate the positive and negative terminals on the amp.

The multimeter has two cables depicting the positive (red) and negative (black) cables. Connect each cable to its corresponding terminals on the speaker and note the resistance in Ohms shown on the multimeter reading.

Check the Amplifier’s Wattage Output

Your amplifier’s manufacturer gives an approved energy output, which should match its speaker’s resistance. This reading is usually indicated underneath the amplifier or in the user manual.

You will need a multimeter to test the resistance and ensure that the measurement begins at 0 and the leads are separated for a correct reading.

Calculate the Correct Alternating Current Voltage

You can use a calculator or simply a sheet of paper and a pen. The alternating current represents the output voltage your amplifier requires to produce the desired results.

The formula for this is: Voltage(V) =√( resistance*wattage)

If the amplifier has more than one gain control, apply the formula for each independently, using the rated wattage multiplied by resistance without dividing.

For instance, if your manual recommends the amp reading at 400 W, but your speaker’s noted resistance is marked at 4 Ohms, then find the solution by multiplying 400 W with 4 Ohms, giving you 1600. As per the formula, the square root comes up to 40 V, and this formula only works for amps with a single gain.

Disconnect All Accessories

This includes unplugging the speakers, subwoofers, etc., from the tested amp. You will also need to disconnect the positive terminal and later reconnect it. Your amplifier should be the only device connected to any power supply.

Turn Off the Equalizer for All Settings

This includes setting the bass, treble, and loudness to zero to avoid distorting the sound waves and to produce a maximum width range.

Set Amp Gain to Zero

In your equalizer, locate all settings, including bass, loudness, and processing, and turn them off. Turning off equalizer settings will prevent sound wave alteration. To achieve zero gain, you will need a screwdriver to turn your amplifier’s dial to zero.

Fix Your Volume Knob

Setting the volume to 75% ensures that the amp receives clear, undistorted sound directly from the speaker.

Disconnect the Speaker From the Amplifier and Play a Test Tune

Remember that you unplugged all devices from the electric supply. Connect your speaker to its power supply and disconnect it from the power amplifier.

Start by playing a test tune on your stereo. The sound usually has a frequency range between 50 to 60 Hertz, which is the specification for most amps.

Ensure the tune keeps playing in a loop by setting the head unit. You can use a test CD or other media to play the tune in a loop.

Set the Multimeter Terminals

Place your multimeter on the amp’s correct speaker outputs. Ensure that the multimeter’s probes are connected to the corresponding terminals: the positive probe to the positive terminal and the negative terminal to the negative probe.

If the multimeter displays an output voltage higher than 6 V, go through the previous stages, specifically 5 to 6 above.

Fix the Gain

You previously set the gain to 0 by turning the knob counterclockwise, and now you need to set it correctly. Turn the gain knob clockwise using a tool like a chisel screwdriver as you carefully watch the multimeter’s voltage reading.

Stop moving the gain once you reach the correct reading. Depending on the sensitivity of your gain knob, move very slowly when approaching the target voltage reading to avoid passing it. This is the last stage for setting the gain on the amp.

Repeat Accordingly for Each of the Remaining Amps

If this is your first time tuning an amplifier, you may not get your desired output on the first try, and you may need to try a few times. If it works the first time, follow these steps precisely for consecutive amplifiers.

Reduce Volume to Zero

Using the head unit, completely reduce the volume to zero, then turn the stereo off.

Reconnect the Cables and Accessories

Put everything back to its original configuration. This includes all the cables and accessories, and then switch everything back on. The cabling may be fragile, so be careful to avoid damaging any connections.

Your speaker will not work when wrongly connected, and this may be frustrating to fix because most of these cables look alike.

You’re Done!

Try playing one of your favorite tunes, but be aware of sound bends. These typically manifest as hissing, crackling, whomping, buzzing, or whiffing sounds. They can even appear in combination depending on the condition of the bend at the time of amp manipulation.

If the results aren’t what you initially imagined, feel free to tune the gain using the steps above to achieve the best possible output. Remember that it is entirely okay to tinker with your system until you find that sweet spot.

Sometimes, your music may seem unbalanced after the first tuning, and your bass may sound off. Fine-tune your amplifier’s low pass filter to delocalize it. The primary purpose of fine-tuning is to smooth out any unbalanced points of your music. Depending on your preference, you can play around with high pass filters to adjust the notes higher or lower.

Frequently Asked Questions

Can I Adjust an Amp Manually?

There are many ways to adjust an amp, including doing it manually. Manual adjustment includes listening to the sound and tuning it to your liking.

However, this isn’t the most efficient method because there may be something off about the sound. Using a multimeter is your easiest bet because you now understand how to do it, and it’s pretty straightforward.

What Hz Should I Set My Bass To?

The bass gets deeper as you lower the Hz, so the best setting depends on your preference. A 20-120 Hz rating is generally okay, and if you have a customized one, don’t go higher than 80 Hz.

What Should I Do if My Amps Have Multiple Gain Controls?

It’s easier if your amp contains an individual gain control. Gain control helps you calculate the amp’s output voltage. In the case of single gain control, find the voltage by multiplying p*R and then finding its square root. For multiple gains, calculate the voltage separately for each amp.

Final Thoughts

This is a detailed guide to help you set the gain on an amp using a multimeter. Other methods give faster results, such as using an oscilloscope to fine-tune your amp. An oscilloscope works by pinpointing all the clippings and distortions from the audio system not identifiable by the human ear.

Although there are many methods you can use when learning how to tune an amplifier with a multimeter, using a multimeter is by far the easiest to master, especially for amateur DIYers.