For newbies in car audio, having an amplifier is the way to a better listening experience. As understood in a general sense, an amplifier lets your speakers and subwoofers perform to their full potential in order to produce high-quality sound production.

The amplifier is a rarely noticed component in a car audio system due to it being placed in hidden spots inside your vehicle. Knowing even a little bit about amplifiers can make all the difference between average and excellent sound quality in your car’s audio system.

Read on to find out everything you need to know about car amplifiers: from learning the basics to understanding their complexities and why all of this information matters when it comes to choosing your own amplifier for your own car audio system.

How a Car Amplifier Works

Amplifiers play a crucial role in the nature of the music you hear in your car as they are essential parts that give your car tunes power and loudness. They enhance the signal that runs through the sound system and plays them through the speakers. Here’s how an amplifier processes the signal:

Stage 1: Preamp

When the head unit produces a weak audio signal, an amplifier amplifies it so that it may move the cones of the speakers and produce sound. A preamplifier processes the signal before it is amplified.

The term “preamp” is used to describe any component in the signal chain that performs signal processing prior to amplification. The low-level output from the head unit’s different sources, such as the CD player or radio tuner, is sent to the amplifier through the preamp.

Bass, treble, and equalization settings all operate on the audio signal at the preamp stage, altering it in order to provide the desired tonal quality. A signal is further processed by the amplifier’s internal input preamp stage once it reaches the device.

Stage 2: Crossover

Crossover circuitry is commonly used as part of the preamp’s processing. It uses an electronic filter to separate the various frequencies present in the audio stream before sending it to the amplifier. A crossover is like a traffic cop for audio signals; it directs signals of different frequencies to different types of speakers so that they can be played back accurately.

There are typically two kinds of crossovers in an audio system. Active crossovers are preamplifier components that split the full-range, line-level signal before it is amplified, allowing individual amplifier channels to focus on a narrower frequency range. Passive crossovers take in an amplified audio signal and separate it into separate channels for each speaker.

“Two-way” speakers use a passive crossover since they feature two drivers in a single enclosure. Typical 6-by-9-inch stock speakers have a huge midrange and a small tweeter, making them 2-way. A modest passive crossover is used to separate the frequencies of the audio signal before it is sent to the speakers.

Passive crossovers have the downside of reducing the output power of a system by attenuating frequencies. For this reason, active crossover circuitry is typically integrated into car amplifiers. It improves the amp’s efficiency and allows the amplifier’s channels to be tailored to particular sets of speakers.

Stage 3: Boosting The Signal

After the signal has been processed by the preamp, the amplifier generates a strong alternating electrical current that is used in conjunction with the speakers to produce audible sound. A car’s stereo system’s amplifiers are typically electronic transistors. An amplifier takes a weak line-level signal from your head unit and amplifies it so it can drive a speaker cone back and forth, producing perceptible sound.

A significant part of an amplifier’s design is dedicated to dealing with the heat produced during this increase. Amplifiers incorporated into head units are small and low power, so they can be safely housed in a vehicle’s dashboard. However, external amplifiers generate even more heat due to their high power output.

An amplifier’s exterior typically includes a heat sink to dissipate excess heat. The amplifier’s heat is dissipated by the heat sink, which is shaped like a radiator for a car, with ridges or “fins” to increase its surface area.

Car Amplifier Power Ratings

Every amplifier has at least two channels, typically left and right. The output of an amplifier is measured in watts per channel. If an amplifier has a higher wattage rating, more power will be sent to the speakers, making them louder.

To get an accurate amp power rating, RMS is a mathematical formula used to quantify the strength of the output signal; its abbreviation is “Root Mean Square.” You won’t need to perform the math for a factory car stereo. Still, you should know that some aftermarket electronics makers inflate wattage figures to make their amplifiers better.

Sometimes, aftermarket car audio manufacturers will advertise “peak” or “maximum” power ratings instead of “RMS” or “continuous” power ratings to confuse customers. When evaluating aftermarket amplifiers, make sure you’re looking for their RMS ratings.

The Car Amplifier Standard: CEA-2006

CEA-2006-A is a voluntary standard for measuring the output power of car audio amplifiers, and the Consumer Electronics Association trade group manages it.

Manufacturers are required to:

  • Express output power as watts RMS
  • Measure with 14.4V DC supply
  • Utilize testing under a 4-ohm load
  • Have 1% or less total harmonic distortion in the amplifier’s output.

The Signal-to-Noise ratio of an amplifier is how much extra noise is present in the amplifier’s output signal compared to the signal being fed to it by a source. It’s the amount of “hiss,” “crackling,” or “popping” you hear when your music is quiet, or there is no music playing. CEA requires that this noise is compared to an output signal at 1 watt. Other amplifier specifications have been standardized for a fair comparison.

Many manufacturers are already using the CEA-2006 rating method, and the list keeps growing. Be on the lookout for the CEA logo the next time you purchase an amplifier.

Car Amplifier Classes

JL Audio Amplifiers

Amplifiers are engineered to convert these electrical signals by a few different methods called “classes.”

There are several different classes of car amplifiers, each with its own characteristics and properties. The most common classes include Class A, Class B, Class A/B, and Class D, among other amplifier classes.

  • Class A

Class A amplifiers are the most basic and least efficient type, but they have the least distortion and the most linear output. They have high sound fidelity but low efficiency. An older style of amplifier that is on 100% of the time and uses a large amount of power.

  • Class B

Class B amplifiers are more efficient than Class A, but they have more distortion and less linear output. They are a little more efficient than Class A and have the potential to suffer from “crossover distortion” as the circuits push and pull between one another. 

  • Class A/B

Class A/B amplifiers combine elements of Class A and Class B, they have higher efficiency and less distortion than Class A, but less efficiency and more distortion than Class B. They are also the most common amplifier used in Hi-Fi systems.

  • Class D

Class D amplifiers are the most efficient type. They have low distortion, and high power output, and is the most common amplifier in use today for car audio applications. Class D amps are more efficient than Class AB, can fit in a smaller case, and as of fairly recent innovations, can rival the audio quality of Class A/AB amplifiers.

Other Car Amplifier Classes

New types of amplifiers, such as BD and GH, are now in development. The latter is superior to A/B and Class D configurations, as it provides the efficiency of Class D while maintaining the quality of an A/B. This is achieved not by turning on and off transistors, but rather by switching between two rail voltages in response to the cyclical nature of the signal. Although Class GH amplifiers are expensive to produce, they significantly cut down on output power loss.

Class BD is about as efficient as class D, which is to say, roughly 80%. Class D’s distortion-free crossover and Class B’s on/off signal relay make filtering problems much easier to deal with.

More advanced forms of amplification beyond class A/B and class D are sure to emerge in the future. Class AB, AD, BD, D, H, and FD are all available from Sonic Electronix.

Despite the classes having marked theoretical efficiencies, each model of an amplifier will perform differently and may or may not live up to the class efficiency. Lower-end brands tend to overpromise power and underdeliver once the amp is installed because of the low efficiency of the amp. When shopping, consider the efficiency at the same level of importance as RMS power.

Car Amplifier Types

The most common way of categorizing car amplifiers is by the channels. Alternatively, you could use classes, but they all eventually fall under channels. The different types of car amplifiers include:

Mono Amplifier

These amplifiers are designed to power one subwoofer or one set of speakers. They are typically used for bass-heavy music and are known for their high power output.

2-Channel Amplifier

These amplifiers can power two speakers or one set of speakers and a subwoofer. They are a popular choice for car audio systems and can also be bridged to power a single subwoofer.

3-Channel Amplifier

A 3-channel amplifier is an amplifier that has three channels, each channel is capable of driving one speaker or one set of speakers. They are a versatile option for those who want to power multiple speakers in a car audio system. However, they are typically less powerful than mono or 2-channel amplifiers, and may not be suitable for extremely large or demanding sound systems.

4-Channel Amplifier

These amplifiers can power four speakers or two sets of speakers and a subwoofer. They are a versatile option for powering multiple speakers in a car audio system.

Multi-Channel Amplifiers

These amplifiers can power more than four speakers and can be used to power a whole car audio system. They are often used in high-end car audio systems.

Installing a Car Amplifier in Your Car Audio System

Sample DIY setup

The majority of amplifiers will provide a complete amp wiring kit. If yours doesn’t, you’ll need a main power wire, an inline fuse (size of the wire and fuse should match what the amp manufacturer suggests), a ground wire, RCA cables, speaker wires, a remote turn-on wire, and connector connectors that are appropriate for your head unit, amp, and speakers (some units may require bare-wire connections).

The size of the amplifier you end up purchasing will be influenced by how much room you have. Your car’s trunk or baggage area is a frequent location for an amplifier. For example, the amp will need to be mounted under, behind, or between the seats if you’re driving a compact SUV.

There’s also the fact that amps get hot, necessitating ventilation systems. Always ensure that they are in a position that will provide the most air circulation. When installing subwoofer speakers in a box, it is recommended that the amplifier be mounted on the side of the box. Put them up high where they’ll get the most ventilation and be safest from harm.

The next step is to plan how to connect the amplifier to the car’s stereo head unit and the battery. The wiring should ideally be hidden under the baseboard moldings along the base of the doors, following any existing wiring looms. There shouldn’t be any interference between the RCA lines and the power wires if they run along the floorboard instead of the ceiling. When running the main power line, it’s essential to remember where the battery is located in the engine compartment.

The primary power cable from the battery must always penetrate the firewall to reach the battery. Always look for an existing wiring loom to follow and use the holes in it. Another hole in the firewall will have to be drilled if this isn’t practicable.

Looking for the best amplifier for your car audio system? Visit Sonic Electronix, the world’s premier retailer of car electronics and consumer electronics. We’ve sold online since 2000 and are the recipients of various customer service and product awards. Check out our selection of car stereos, amps, subs, speakers, and more from Pioneer, JVC, NVX, Belva, Kicker, Rockford Fosgate, Cerwin-Vega, and more.