Car Amplifier Guide

Amplifiers take the signal from the stereo and use their own power source to change it into a more powerful signal for the speakers. The more power the amplifier delivers, the better the sound from the speakers. Granted, most aftermarket stereo units have at least twice the power of a stock radio, but many times, it’s simply not enough. If you’re going to have a bunch of sub woofers and component speakers in your vehicle, an amp is most probably a good idea.

Let’s say you’ve invested in a new set of upgraded speakers and also in a sleek new stereo receiver unit. You’re about to hear your music in superior ways. However, your car might not be doing your custom audio system justice — and your radio’s built-in amplifier might not supply ample power to the new components.

This is why you may need an external amplifier, or amp, as your audio setup becomes more elaborate. 

In most cases, you might want one amp for all the speakers in the car, which means you’ll need multiple channels on the amp — each channel drives one speaker. Since most of the cars have four speakers, four-channel amps are the most popular. Five or six channel amps will provide you even more options. If you have only one subwoofer and no other high-powered speakers, you only need a one-channel amp. Otherwise, the subwoofer might probably require its own amp.

It is necessary to match up your stereo and speakers with the right amp. You’ll see two power ratings while shopping for a car amplifier: root mean square (RMS) power, and peak power. Here’s what they are:

  • RMS: The amount of continuous power that an amplifier produces and measured in watts. The RMS power on your amp should always match with the RMS power rating on your subwoofer and speakers. The higher the RMS rating, the louder and cleaner your music sounds will be.
  • Peak power: The wattage a car amplifier has for brief sound increases. This number is always higher than the RMS power.

It’s necessary to make sure the RMS number on your amp matches the rating on your speakers. If the numbers don’t match, your speakers could be underpowered, or even overpowered. If they’re overpowered, they will overheat and get become damaged.

Common Problems, Symptoms and Solutions

New installed head unit has no power

If you find that the power cuts out in your recently installed aftermarket head unit, it’s highly likely that the head unit is not receiving 12V.

Another cause for this head unit problem could be that your amplifier might have switched into protection mode. There are two reasons for this. First, power produced by the alternator is too much for the amplifier and it has to protect itself from damage. Second, the battery is unable to provide the audio system with constant voltage.

The most common symptom for this problem is the head unit cuts out and it comes back after a while.

No bass coming from car speakers

This is a car stereo problem usually occurs when factory speakers are being upgraded or aftermarket speakers are being installed or being repaired. What can make speakers to lack bass?

For bass to be generated, speakers need to push air at the same time. The “no bass” problem might occur when one speaker pushes while the other pulls air. This mostly takes place when the speakers are out of polarity.

Another reason for this is that aftermarket speakers are heavier and harder than factory speakers. These speakers improve the quality of your car stereo but eat up the bass of the car’s factory speakers.


You will not hear any bass at any volume level.

How to solve this ‘no bass’ car stereo problem?

Check whether the speaker wires are connected to the stereo amp and head unit appropriately or not. The positive (+) terminal of the speaker needs to be connected to the positive terminal of any other component, including the battery. Same goes for the negative (-) terminal.

Another potential solution might be to install an external amplifier. Some people choose to have a head unit upgrade to solve the no bass problem. The bottom line is that your car stereo needs a thing that puts in more watts.

Unwanted noises coming from the car audio system

Hearing mysterious noises from car audio system is a frustrating experience. Nearly all drivers has encountered car stereo noise at one time. There are a number of sources of unwanted noises but here are some of the most common ones:

Alternator whine: The most common car stereo noise. This often happens when ground for either the head unit or speaker’s amplifier is poorly chosen. Poor condition of the charging system and connections between the audio system components as well as the battery can also result to alternator whine.

Symptom of alternator whine: You hear a noise has fluctuations with the RPMs of your vehicle’s alternator. Alternator whine rises and falls with the engine’s speed in a pretty annoying way.

Accessory pop: This noise is usually connected with a particular electrical event. Usually, accessories like headlights, windshield wipers, turn signal and brakes draw high current and make a voltage spike that then travels to the audio system.

Symptom: A sharp pop sound will be heard when you switch on or press the high current car accessories like the ones listed above.

Speaker popping and crackling: It’s usually caused by breaking down due to old age or poor input quality or bad radio connection.

Symptom:  Speaker crackles when the engine is turned on and when the car will be in motion.

Getting unwanted noises off the car stereo

For alternator whine, find the component that’s making noise and re-grounding it.

A clean, bare chassis metal will be the ideal grounding. Also ensure that the charging system is in its possible best condition. All connections (like battery posts, alternator connections, head unit, amplifiers, signal processors, and ground strap) should be made secure.

To clear the noise due to accessory pops, add a small bi-polar capacitor between the power wire of the accessory producing noise and its ground. The capacitor will absorb the power surges and will be preventing their transfer to the car’s audio system.

If the speaker is popping and crackling, swap the channel and check whether the noise will seize or not. Otherwise, crackling that happens all the time no matter what channel the radio is on means that the speaker is broken and has to be repaired or to be replaced.

Sound just suddenly cuts off

Sound cuts usually occur when the amplifier is getting overheating or a speaker wire has become loose. Amplifiers normally generate a lot of heat especially when music is played at high volumes for long periods. To manage this amount of heat, the amplifier needs to get enough airflow.

This problem is specified by sound from car speaker(s) suddenly cutting off and coming back after a short while.

To solve the problem, make sure that there’s enough airflow where the amplifier is mounted.
The airflow keeps the amp cool all the time and prevents sudden sound cut offs. Also check the speaker wires to make sure that they are properly connected.

Car stereo problems occurring due to poor grounding

The majority of non-equipment related audio problems result from poor chosen ground points. Apart from alternator whine, poor grounding can make the amplifier to clip.

Poor grounding can make the amp to cut in and out. When the car stereo is turned up, the amps pull more of the current. If the system doesn’t have a reliable ground the amp can’t pull the needed current. This usually sends the amp into clipping.

Symptoms of poor grounding: Alternator whine; and the audio system produce some crappy types of sound.

Proper grounding on car stereo

While checking the integrity of other connections, always remember that grounding is of utmost importance. If you install a big car audio system, it will require a bigger ground. It’s also important to remember is that grounds should be on the car’s chassis. Many people make a mistake to use the negative battery post as a ground for the car audio system. This is a terrible place as the entire ripple from various items including the alternator travels through this particular point. Using it invites all the noise from these items into the sound system.

The stereo is the main part of the music system of the car. Without it, your in-car entertainment is quite rarely enjoyable. For all the music lovers, especially, driving a car without stereo is unimaginable. The truth is that lack of maintenance can result to your car stereo showing the problems discussed above. To make sure your sound system is working the way it should, there’s requirement for a full diagnostic of the system. Installation faults as well as other causative issues will be addressed and the system will definitely run in a proper manner to give you the best sound quality.

Video of How you Can Change Your Car’s Amplifier

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