Car Amplifier Classes : Which One Do I Need?

When it comes to upgrading the car’s audio system, choosing the right amplifier has to be your first decision.

Because they enhance the audio signal to power the speakers, resulting in a clearer, louder, and more detailed sound.

However, with so many different amplifier classes available, it can be challenging to know which one is best suited for your audio setup.

Each amplifier class has unique benefits and drawbacks that can significantly impact the performance of your system.

In this article, we’ll take a closer look at the different types of amplifier classes, what sets them apart, and which class is best suited for your specific audio needs.

What Is An Amplifier Class And How Are They Classified?

The Amplifier Class refers to the method of combining power and signal in an audio amplifier. The efficiency and sound fidelity of an amplifier are influenced by the specific class used, as different designs have varying characteristics.

Amplifier classes are classified into different types based on the response they exhibit when the signal passes through them.

There are several amplifier classes available however six categories are most prominently used in car audio systems that include Class A, Class B, Class AB, Class D, Class G, and Class H.

Comparison Chart Representing Different Amplifier Classes

Amplifier Classes Class A Class B Class AB Class G Class H
Fidelity High  Low  High  High  High 
Efficiency Poor Good Good High High
Size Large  Small Small Small Large
Distortion Low High Lesser Low Low
Price Point Expensive Reasonably Priced Reasonably Priced Reasonably Priced Expensive

In-Depth Description of Different Amplifier Classes For Car Audio Systems

Though the power amps of these classes perform the same function, they actually operate under similar basic principles. However, the car amp classes among them are not equal. The car audio amplifier classes explained below help you understand their differences and make an informed decision. 

1. Class A Amplifiers

This is the most basic one among different car amplifier classes. They have a single switching transistor used to amplify the input signal. The main benefit of this type of amplifier is its construction which generates low distortion levels, thereby ensuring excellent sound clarity. 

On the downside, they really use up more energy and generate quite a lot of heat during operation. Higher heat sink space is needed to manage the heat generated, making them bulkier. In addition to that, they are expensive and higher in maintenance. They are only suitable for low power levels and low signal amplification purposes.


  • Accurate sound reproduction
  • Low distortion levels
  • Excellent sound quality


  • A lot of heat generation
  • Not compact

2. Class B Amplifiers

Class B amplifiers are designed to be more efficient than Class A amplifiers. They achieve this by splitting the audio signal into two segments and amplifying each segment separately using a pair of complementary transistors. It means that each transistor is responsible for amplifying either the positive or negative segment of the signal.

The advantage of this setup is that each transistor only needs to amplify half of the waveform, which results in less heat dissipation and increased energy efficiency. However, this comes at a cost. The switching between the two transistors can cause distortion and noise in the output signal, affecting the overall sound quality.

To minimize distortion and noise, Class B amplifiers require a minimum of two output devices per channel, and these devices must be biased to operate near the cutoff point. When no input signal is present, both output devices are switched off, improving efficiency.

Class B amplifiers are more cost-effective to manufacture than Class A car amplifiers and are helpful in applications where efficiency is a primary concern. However, they may not be the best choice for applications requiring high-quality audio reproduction, as they can produce higher levels of distortion than Class A amplifiers.


  • More efficient
  • energy-efficient
  • High-quality audio reproduction


  • Higher distortion
  • Decreased sound quality

3. Class AB Amplifiers

Class AB amplifiers are designed to balance the sound quality of Class A amplifiers and the efficiency of Class B amplifiers. They achieve this by using two sets of output transistors, each handling the audio signal’s positive and negative portions. The output transistors are biased to operate in the Class A region, which reduces distortion and improves efficiency compared to pure Class A amplifiers.

Additionally, an optimum bias current for each amplifier reduces the crossover distortion of Class B designs. While they still generate some heat, they are less prone to overheating than pure Class A amplifiers.

They are commonly used as full-range amplifiers in-car audio systems due to their practicality and balance between efficiency and sound quality. 


  • More efficient compared to class A
  • Good sound quality
  • Less distortion compared to class B


  • Less distortion compared to class B
  • More distortion compared to class A

4. Class D Amplifier

Class D amplifiers are highly efficient amplifiers that use a switching transistor to create a pulse-width modulated (PWM) output signal. These amplifiers consume less power and generate less heat than other amplifier classes, making them popular for car audio systems and portable audio equipment.

Although Class D amplifiers can generate high-frequency noise due to the switching nature of the output signal, modern designs have addressed this issue to provide high-quality sound reproduction. 

Class D amplifiers are smaller, lighter, and run cooler than other amplifiers with the same power output, making them a popular choice for applications where size and weight are critical factors. They are even used in high-end home audio systems where they can provide incredible sound reproduction when appropriately tuned.


  • Compact size
  • Lots of power
  • Very little heat
  • Highly efficient


  • Potential distortion at high frequencies

5. Class G Amplifier

Class G amplifiers are a type of amplifier that offer a combination of benefits from class AB biasing and an adaptive power supply. They are particularly suited for high-power applications like high-end car audio systems. 

These amplifiers work by switching between two power supply rails based on the input signal’s amplitude, resulting in increased efficiency and reduced heat dissipation compared to class AB amplifiers. It is achieved by an integrated buck controller that adjusts the voltage rail based on the audio signal level, optimizing efficiency at each output level.

One of the key advantages of class G amplifiers is their ability to produce better sound quality than class D amplifiers. This is because they generate less high-frequency noise. As a result, class G amplifiers are an excellent choice for car audio systems that require high power output while remaining efficient and generating minimal heat.


  • High audio quality
  • High-efficiency operation
  • Less wasted heat energy


6. Class H Amplifiers

Class H amplifiers are slightly modified Class G amplifiers but offer some impressive advantages. Instead of relying on just two power supply rails, Class H amps utilize multiple supply rails that switch seamlessly depending on the input signal amplitude. They can achieve even higher efficiency and generate less heat than Class G amps. 

Their variable boost level sets Class H amplifiers apart from their Class G counterparts. It allows the output to operate with enough headroom to maintain low distortion while achieving maximum output efficiency. You can expect outstanding sound quality with these amplifiers, even at high power levels. So, if you’re looking for a powerful and efficient audio amplifier for your professional audio system, Class H might be just what you need.


  • Maximum efficiency
  • High-quality sound output


  • Cross over distortion
  • More complexity

How to Choose the Right Amplifier Class for Car Audio?

Since there are multiple amplifier classes, choosing the right one suitable for your car’s audio system can be a confusing task. If you are at a crossroads, the information below will help you make the right decision.

1. Power Requirements

The first factor to consider while selecting an amplifier class is the power requirements of your system. Determine how much power your speakers require to function optimally and choose an amplifier to deliver that power.

  • Class A amplifiers have high power requirements and are the least efficient. The average power consumption of Class B and AB amplifiers ranges from 20 to 200 watts. However, some high-end Class B and AB amplifiers can consume up to 1000 watts of power.
  • Class B and AB amplifiers have high moderate power requirements and are more efficient than Class A. The average power consumption of Class B and AB amplifiers ranges from 20 to 200 watts. However, some high-end Class B and AB amplifiers can consume up to 1000 watts of power.
  • Class G and H amplifiers have lower power requirements and are more efficient than Class B and AB. The average power consumption of Class G and H amplifiers ranges from 10 to 100 watts. However, some high-end Class G and H amplifiers can consume up to 500 watts of power.

2. Sound Quality

Sound quality is a crucial factor to consider when selecting an amplifier class. It refers to the clarity, accuracy, and fidelity of the audio produced by the amplifier.

Class A and AB amplifiers are known for their high sound quality due to their low distortion and noise levels. Class D amplifiers can produce high-quality sound but sometimes have higher levels of distortion and noise, particularly at high frequencies. Class G and H amplifiers are known for their high efficiency and low heat dissipation, but the sound quality can vary depending on the specific design and components used.

When selecting an amplifier class based on sound quality, it’s important to consider personal preferences and the specific application, such as the type of music being played and the listening environment.

3. Efficiency

Efficiency is the ratio of the total amount of electrical power an amplifier draws from the power source to the amount of electrical power it converts into useful output power. An efficient amplifier will convert more input power into usable output power and waste less energy as heat.

Different amplifier classes have different levels of efficiency. 

  • Class D amplifiers are the most efficient, with over 90% efficiency
  • Class A amplifiers are the least efficient, with around 20-30% efficiency. 
  • Class B and AB amplifiers fall in the middle, achieving 50-70% efficiency
  • Class G amplifiers typically have efficiencies in the 70-80% range
  • Class H amplifiers can have efficiencies up to 90% or higher.

In summary, Class D amplifiers are the ideal option if efficiency is paramount. Class G or H amplifiers, however, might be a good compromise if you need a high power output and low distortion but also want to place efficiency first.

4. Distortion

Distortion refers to unwanted changes in the original sound signal during amplification. In general, lower distortion means better sound quality.

  • Class A amplifiers typically have the lowest distortion
  • Class B amplifiers have higher distortion than class A amplifiers
  • Class AB amplifiers have lower distortion than class B amplifiers but higher efficiency than class A amplifiers. However, they still have some crossover distortion.
  • Class D amplifiers have the highest distortion of all amplifier classes,
  • Class G and class H amplifiers have lower distortion than class D amplifiers

5. Price

Your budget is important when choosing the right amplifier class for your audio car system. Class D amplifiers are the most affordable due to their simpler design and lesser power output. In contrast, Class A amplifiers typically have the most expensive price tag because of their complex design and high power output. Class B and AB amplifiers are usually in the middle, while class G and H amplifiers can range from the middle to the top depending on their features and power output. It is important to weigh the price in connection to the amplifier’s intended use and desired power output before purchasing.

Note : To find the suitable class amplifier for your car audio system, it is essential to consider the factors mentioned above. We recommend researching and comparing the features of different amplifier classes. You can also consult professional car audio installers and car accessories experts to help you choose and install the car amplifier.

Which Amplifier Class Should I Choose For My Car’s Audio System?

When it comes to car audio amplifiers, selecting the most suitable amplifier class is influenced by various factors such as the desired power output, sound fidelity, efficiency, distortion levels, and available budget.

An A/B amplifier is often the best choice for powering your main speakers. This amplifier provides high-quality sound without distortion in high tones, making it ideal for coaxial or component speakers. Additionally, A/B amplifiers typically don’t require large amounts of power to drive car speakers, so you don’t need to look for an amplifier with hundreds of watts of RMS per channel.

However, a different type of amplifier is needed when it comes to powering a subwoofer. Subwoofers require high power output to reproduce low-frequency sounds, but the sound quality is less concerned for these frequencies. Some distortion can even be desirable to achieve a “punchy” bass sound.

For subwoofers, class D amplifiers are often the best choice. These amplifiers are highly efficient and powerful, making them ideal for providing the high-power output needed for subwoofers. Class D amplifiers use pulse-width modulation to switch the power supply on and off rapidly, allowing them to achieve high power output with minimal power loss.

Class A amplifiers can generate good quality sound but are premium-priced and not so efficient. And finally, Class H and G amplifiers ensure efficient audio output quality and high efficiency, but they are unsuitable for all kinds of power necessities. We recommend you consider these factors or consult a professional for assistance.


There is no rule or guidance for choosing the appropriate amplifier for a car audio system. It is essential to check out the options and perform your research to make an informed choice.

Given the numerous variations of each type of amplifier and the varying price points, choosing the right option without proper knowledge is difficult. We have mentioned different car amplifier types in this article for your reference so that you can choose the right option based on your preferences.

Car Amplifier Classes – FAQs

 1.  What are the different classes of car amplifiers?

Ans: There are several class car amplifiers in the market, including Class A, Class B, Class AB, Class D, Class G, and Class H. The choice of a car audio system depends on various factors, such as power requirements, good quality expectations, and budget.

2. Class D vs Class AB car amplifier – which one is better?

Ans: Class D amplifiers can produce high-quality sound with less power consumption and less heat. It can benefit audio systems in cars and other places where power efficiency is a top priority. The best Class AB car amplifiers, on the other hand, are renowned for their superior sound quality, particularly at low to moderate power levels. They are also better for critical listening applications like studio monitors or home audio systems because they have lower distortion levels. As a result, the specific requirements and priorities of the audio system ultimately dictate the choice between a class D amplifier and an AB amplifier.

3. Which is better Class A or Class B amplifier?

Ans: Class A amplifiers are known for providing the highest sound fidelity but are the least efficient design. Class B amplifiers are more efficient than Class A but often suffer from high distortion levels.

4. Are Class D amplifiers any good?

Ans: If you desire a high-quality audio system without sound distortion such as clicks, pops, or hisses, then the best class d car amplifier may be the right choice. Class D amplifiers are highly efficient and offer good sound quality, making them popular. Unlike other amplifier classes, a class D amplifier has no specific switch. However, it is essential to ensure that the power transistor and other components in the amplifier are correctly matched to maintain high product quality. If any components are not correctly matched, it can significantly decrease the overall product performance.

5. Which amplifier class is the best?

Ans: It is hard to determine a single amplifier class as the best because they all have advantages and disadvantages. The best choice usually depends on your car’s audio system and personal preferences. You can refer to the information provided in this article to make the right decision.

6. What are the disadvantages of Class D amplifiers?

Ans: Class D power amplifier speakers may experience distortion due to various reasons. Matching the power transistor with other components is crucial for the quality of the entire product, as there is no dedicated switch for class D power amplifiers. The output circuit of a class D power amplifier may experience dead bands, resulting in issues with the signal.

7. Are Class D amplifiers noisy?

Ans: Class D amplifiers are not loud, but their switching mechanism can create EMI that could disturb surrounding devices or components. Manufacturers generally integrate features into car amplifier class D designs to lessen these effects and the likelihood of noise.

8. Where can I use a Class A amplifier?

Ans: Class A car amplifiers are commonly used in applications that demand high-quality audio performance with minimal distortion at low power levels. For instance, they are widely used in radio and guitar amplifiers where audio quality is critical.

9. What is a Class D amplifier used for?

Ans: Class-D amplifiers are highly sought after for their compact size and high efficiency, making them an ideal choice for home theatres and other audio systems.

10. What is a Class G and H amplifier?

Ans: Class G and H amplifiers are both versions of Class AB amplifiers, which are a type of analog electronic amplifier. They take multiple power supply rails to improve efficiency by switching between voltage levels depending on the input signal level. Class G amplifiers provide better efficiency at lower power levels, while Class H provides efficiency at higher power levels. Class G and H amplifiers are commonly used in audio applications where high efficiency and low distortion are important, such as in professional audio equipment, home theatre systems, and PA systems.

11. What class of amplifier is the best for subwoofers?

Ans: Class D or digital amplifiers use a high-frequency switching process to operate with smaller power transformers, making them ideal for subwoofers where interior space is limited.

12. Why do Class A amplifiers sound better?

Ans: Class A car amps are favored for their accurate sound quality due to their single transistor operation, low output impedance, and minimal harmonic distortion. However, they tend to be less efficient than other amplifier classes, resulting in higher power consumption and heat dissipation. Therefore, they are typically used in high-end audio systems where sound quality is the primary concern.

13. What is the drawback of a Class B power amplifier?

Ans: Class B amplifiers generate crossover distortion and have higher distortion levels than Class A amplifiers. They require a stabilized power supply as the current supply changes with the signal. Additionally, it is challenging to find two complementary transistors with the same characteristics, which can affect the amplifier’s performance.

14. What is the benefit of Class B over Class A?

Ans: Class B amplifiers feature a push-pull design in which one transistor increases the positive half of the input signal. In contrast, the second transistor increases the negative half, making them more efficient than class car amps, with only half of the input waveform cycle used by each transistor. As a result, less power and heat are produced.

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