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Which Amplifier Class Is Best for Car Audio?

If you want the best sound out of your car audio system, you’ll need to choose the suitable amplifier class.

But with all the different classes available, which one is best for your car? Let’s find out.

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If you’re looking for the best sound quality, then a Class A amplifier is the way to go for the best. On the other hand, a Class AB amplifier may be a better choice for a more affordable option. And if you’re looking for the most efficient amplifier, then a Class D amplifier is the way to go.

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Tip: When you are on a budget, it is better to look at a compact D-class multichannel amplifier that will be good enough for the entire system without needed investments into the A/B amp for the speakers and a strong D class for the subwoofer.

An excellent example of the compact D-class amp is the Rockville dB55, with a built-in 12-band equalizer and variable bass boost for the subwoofer channel.

In the article below, I will detail the different amplifier classes and how to choose the right one for your car audio.

What Is Amplifier Class?

An amp class is simply the classification of how an amplifier operates. There are four main amplifier classes: Class A, Class AB, Class D, and Class G.

Class A car audio amplifier amplifiers are the oldest and most inefficient types. They produce the best sound quality but are also the most expensive and require the most power to operate.

differences between car amplifier classes

What Are the Differences Between Amplifier Classes?

All three types of amplifier classes can be divided into two main groups:

  • A, B, and AB amplifiers with constant energy consumption, even if no signal is transferred to them.
  • D class amplifier consumes energy only when transmitting a signal to the speakers.

A Class Amplifiers

The pure class A car amplifier is “on” nonstop and consumes the whole supplied energy, transferring it to heat.

For example, when you have a 100W class “A” amplifier in a car, and while you drive, it runs at its full capacity and consumes 100W of energy all the time, and it does not matter if you are listening to the music or not.

This energy is transmitted to the heat. In an ideal situation, if this amplifier were 100% efficient, it would supply a 50W per channel, assuming this is a stereo (or two-channel) amplifier, but in this case, it is zero.

That means the “A” class amplifiers are inefficient unless you listen to music nonstop while driving your car. Then efficiency is a little higher, but still very low due to the amount of heat produced.

When you turn your radio on, the output power of 100W energy changes from the heat and goes immediately to the speakers.

Now, this energy is transferred into the sound you want, and the sound quality from the A-class amplifiers is crystal clear.

The constant energy consumption in an “A” class amplifier is to keep transistors, or any other output devices turned “ON” all the time. This reduces the noise created by the transistors and makes the highest-quality sounds.

Class A amplifiers produce the highest sound quality and, at the same time, a lot of heat.

Unfortunately, because they are so inefficient (in a range of around 25% if you are lucky), it costs a lot of money to produce a powerful “A” class amplifier. They are, therefore, the most expensive of all car amplifiers.

For example, one of the best car amplifiers is the 2x100W Mosconi Dynamic, built with full A class, and it costs over $2.900.

Class B Amplifiers

The class B amplifier is an amplifier that uses two transistors, and these are turned on and off alternately.

This way, only half the time, transistors are “ON,” which means they do not produce that much heat. Because of this, although still analog, class B amps are slightly more efficient than class A but less than amplifiers in the D and G classes.

The sound quality of the class B amplifier is not as good as the “A” amplifier mainly because of their much higher distortion.

The main advantage of these amplifiers is that they are much cheaper to produce than “A” class ones, but they are not as commonly used in car audio systems.

AB Class Amplifiers

Although class AB has the same principle as class A to keep an amplifier always on, 100W class AB amps will not consume a constant 100W energy.

Continuous energy consumption depends on the model, ranging from 2W to 20W, so it is more like running on “standby” mode.

The great thing is even if you do not listen to the music, the AB amplifier consumes this power and operates in class “A” mode. This energy is needed to keep all components powered and ready for any signal input.

When you turn the radio on, this energy is immediately transferred into a sound. However, when you listen to quiet music, it can happen that the AB amplifier will continue to consume this basic 20W and will never switch to the B class.

But, when you increase the volume and listen to loud music, the amplifier’s consumed energy will rise to the max and drop back to the minimum level when you turn the radio off.

This technology’s advantage is the lower signal distortion, which makes a music signal clear, and these amplifiers produce much less heat than the pure “A” class. They are also much cheaper than pure A-class models but still expensive.

The main disadvantage of AB amplifiers is their efficiency which could be better if they were digital amplifiers. However, it is higher than A-class amplifiers, and depending on the model, it varies between 50% and 70%.

The other disadvantage of AB amplifiers is their size and weight.

D Class Amplifiers

Class D is a different way of generating energy and powering loudspeakers. The primary term for the class D amps is Pulse Width Modulation, but what is this?

According to Wikipedia, “Pulse width modulation (PWM), or pulse-duration modulation (PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts.”

In other words, these are signals at regular frequencies. For example, for 100Hz frequency, the D class amplifier will switch “on” and “off” every 1/100 of the second. With sounds of the 4000Hz frequency, the amplifier turns on and off 4000 times per second!!!

Because transistors in “D” class amplifiers are either on or off, they run at high efficiency close to 90% for the top models, creating very little heat at the same time and the most significant disadvantage of the D amplifiers at the same time.

The D class’s most significant disadvantage is that when transistors switch between “on” and “off” thousands of times per second, they create a lot of noise that must be eliminated.

Otherwise, the noise will be transmitted to the speakers, but I would rather listen to music than the buzzing sounds.

To eliminate these noises, “D” class amplifiers are equipped with a low-pass filter made from many inductors and capacitors.

Unfortunately, the noise is not the only issue related to constant turning on and off.

A more common issue, especially in the older or modern cheaper amps, is their interference with AM/FM radio frequencies. This is because the amplifier works on the same principle as a radio transmitter.

To eliminate this problem, many D-class amplifiers are equipped with audio signal filters that must be placed as close to the amplifier as possible. 

At the same time, the amp should be as far from the stereo as possible to avoid any sound quality loss.

Another problem with modern class D amplifiers is their sound distortion, mainly affecting high-frequency sounds. This is the main reason why D class amplifiers are not the best choice when you value clear music more than anything else.

To sum up, D class amplifiers are the cheapest, smallest, and most efficient option creating the least heat.

However, although they are the best performance amplifiers, their disadvantage is that the sound quality compared to the A or AB class can eliminate class D from many car sound systems, making them primarily usable for subwoofers where the sound quality is less critical.

Which Class Amplifier Should I Choose for My Car?

Choosing the suitable amplifier is not straightforward due to the number of types.

When searching for the amplifier to power the speakers, the best choice, as I already mentioned, is the A/B amplifier that provides a high sound quality without distortions in high tones, and it does not matter if you will use it for coaxial or system speakers.

Car speakers usually do not need hundreds of watts of RMS per channel, so A/B is the best option if you want to listen to high-quality music.

For the subwoofer, the situation is a little different. Subwoofers need high power output, and while an A/B amplifier can still supply this, there is little need for sound quality in the frequencies produced by the subwoofer.

Subwoofers work at the lowest range of the tones, starting from around 20Hz up to 200Hz at the most, and for these frequencies, the class “D” amplifiers will be the best because they are powerful and efficient.

Many mono amplifiers are made in class D because of this reason. They supply subwoofers with a high power rating and are much cheaper than AB-class amplifiers.

A/B/D Class Amplifiers – Comparison

Now, let’s compare all four mentioned amplifier classes to see which is best for you.

Class “A” Amplifier:

  • Produces the best sound quality
  • is the biggest and heaviest amplifier
  • is the most expensive amplifier
  • runs at low efficiency, around 20-30%
  • creates a lot of heat

Class “B” Amplifier:

  • produces highly distorted sounds
  • is smaller and lighter than a class A amplifier
  • is cheaper than a class-A amplifier
  • runs at higher efficiency, around 50%
  • still creates some heat

Class “A/B” Amplifier:

  • Best sound quality
  • Larger and heavier
  • Cheapest from all analog car amps
  • Run cooler

Class “D” Amplifier:

  • Most efficient
  • works in digital mode
  • Smallest and lightest
  • Cheapest
  • Can create interference with AM/FM radio frequencies
  • Created sounds can be distorted in high frequencies.

What Class Amplifier Is Best for Subwoofer?

Powering subwoofers can be tricky, especially if you have a large DVC driver. Generally, you will want an amplifier stable at 2 ohms, which is a load of most subwoofers.

The best amplifier classes for subwoofers are D and A/B for less powerful systems. Class D amplifiers are more efficient than A/B amplifiers, meaning they require less power to produce the same volume.

If you have a powerful subwoofer system, you may need an amplifier that is stable at 1 ohm, and in this case, there is no other than a class “D” option.


The optimal amplifier class for car sound systems are the AB and D amplifiers:

A/B class is best for the speakers and surround systems because of low distortion levels and high sound quality.

Class D amplifier is the best for subwoofers because it is powerful, efficient, and cheapest per wattage.

I hope this article helped you to understand amplifier classes and make the right decision for your car sound system. If you have any questions, shoot me a message.


How to Balance the Power of Two Amplifiers in the Car?

When there is more than one amplifier in the car, for example, one for a subwoofer and another for the rest of the speakers, or when speakers are powered directly by the head unit, it is essential to create the right balance between these two sound systems in the car.

The ideal balance should be 50/50 or 60/40, which means the RMS power of the subwoofer amplifier alone, should be over half of the total RMS from all installed speakers.

For example, when a car radio has the power 4x30W RMS, ideally, the amplifier for the subwoofer will produce a total of between 120W and 180W. Or, when you use a 4x200W amplifier for the speakers, the amplifier for the subwoofer should be between 800 and 1200W.

Do I Need an Amplifier for Door Speakers?

External amplifiers in the car positively impact the music dynamic and sound quality. However, amplifiers built into head units have several weak points, which external amplifiers can compensate for:

  • With the external amplifier, you can listen to music with better sound quality and without distortion, especially at higher volumes.
  • Many multichannel amplifiers allow you to connect both speakers and the subwoofers at the same time.
  • New and more powerful than factory speakers will need more power than the head unit can produce