Amplifier Buying Guide

What does an amplifier do for your stereo? To keep it simple, an amplifier takes a weak signal and makes it more powerful. Think of the amplifier as the heart of the system, it is the device that provides the power to move the speakers. If your speakers are underpowered they are not working to their maximum potential, which leads to poor sound quality and may even harm your speakers. For the most part factory installed stereos provide very little power output to drive your speakers. A properly matched amplifier/speaker combination will produce a full, rich sound where you can hear all of the nuances of the media that you are listening to.

If you are thinking about adding an amplifier to your car stereo because your system has lost its luster, but are still using your factory installed speakers, you may want to start by replacing your factory speakers. Typically factory speakers are not of the highest quality and tend to wear out over time.

Power Rating: Amplifier power ratings are categorized in two measurements.

  • RMS (root mean square) Power: The measurement of the amount of Continuous Power the amplifier can produce comfortably. This is the rating that industry professionals are most concerned with, and it is a more concise reflection of the amount of power the amplifier is capable of producing. Once the amplifier has surpassed its RMS Power rating it will begin to generate heat, distort, and may cause damage to the unit itself.
  • Peak Power: How much power the amplifier can produce for a very, very short period of time before damage or failure occurs. For the most part this rating is discarded by industry professionals, and it is consider more of a “marketing” power rating. Sure the amplifier may be capable of producing the claimed amount of power, but it will not sound pleasant and it will not be long before the amp shuts off or blows. Therefore it is deemed as a useless measurement of power output and is not considered a worthy rating.

When looking for an amplifier, be sure that you are taking note of the RMS power rating and not the Peak power rating. There are numerous amplifiers on the market that claim that they will produce thousands of watts of power for very little money. It may sound too good to be true, and that’s because it is. These types of amplifiers are built with inferior electronic components. Sure they will amplify your signal, but not to the numbers that they claim. Inexpensive amplifiers tend to produce a lot of signal noise and typically have a very short life span. If you are looking at an amplifier that is rated at 2500 watts peak power and 800 watts RMS power then it is really an 800 watt amplifier.

CEA 2006 Compliant Amplifiers

It is good practice to look for amplifiers that are CEA 2006 compliant. There was a time when car audio amplifier manufacturers could rate their amplifiers any way that they saw fit. This led to unsubstantiated claims of tons of power in a small package for very little money. In 2006 the Consumer Electronics Association (CEA) developed a standardized means of testing and rating an amplifier’s power output. When you compare an amplifier that is stamped with the CEA logo to another CEA amp, you know that these 2 amplifiers were tested the same way, and that you are comparing apples to apples.

Amplifier Configurations: Amplifiers come in a number of different configurations, which one is the best for your application depends on the amount of channels that you require. A channel is the powered signal that an amplifier sends to a speaker. The amplifier’s power rating is listed as watts per channel at a specific ohmage. Typically the amp is configured to one channel per speaker but there are exceptions.

Typical Configurations For Amplifiers:

Mono Block Amplifier

1 Channel (Mono Block) Amp Scenarios:

  • 1 Speaker - Primarily used for subwoofers; typically this style of amplifier is not capable of full range audio, and they are engineered to deliver loads of power to low frequency speakers.
2 Channel Amplifier

2 Channel Amp Scenarios:

  • 2 Speakers - Left and Right
  • 1 Speaker (Mono) - Subwoofer (bridged*)

* Amplifier must have bridging capability.

3 Channel Amplifier

3 Channel Amp Scenarios:

  • 3 Speakers - Left and Right + 1 Subwoofer
4 Channel Amplifier

4 Channel Amp Scenarios:

  • 4 Speakers - Front Left, Front Right, Rear Left, Rear Right
  • 3 Speakers - Front Left, Front Right and Subwoofer (bridged*)
  • 2 Speakers - Front Left and Front Right (bridged*)

* Amplifier must have bridging capability.

5 Channel Amplifier

5 Channel Amp Scenarios:

  • 5 Speakers - Front Left, Front Right, Rear Left, Rear Right and Subwoofer
  • 3 Speakers - Front Left, Front Right and Subwoofer (bridged*)

* Amplifier must have bridging capability.

6 Channel Amplifier

6+ Channel Amp Scenarios:

  • 6 Speakers - Front Left, Front Right, Rear Left, Rear Right and 2 Tweeters
  • 4 Speakers - Front Left, Front Right, Rear Left, Rear Right and Subwoofer (bridged*)

* Amplifier must have bridging capability.

Other Things To Consider When Choosing An Amplifier

Ohms (Ω): Also reffered to as impedance. This is the measurement of resistance that the speaker adds to the circuit. In car audio, typically the full range, mid range speakers, and tweeters are almost always rated at 4Ωs.

It is very important to match your amplifiers impedance to your speakers impedance. Since most multi-channel, full range amps are configured for 4Ωs, this is mainly a concern when dealing with subwoofers.

When and amplifier meets very little resistance it then begins to produce more output (power) than it was designed for and will cause damage or failure to the unit. Conversely, if you power 8Ω speakers with a 4Ω amplifier you will have reduced output.

For example, connecting an amp that produces 1000 watt at 2Ω to 2 subwoofers that are rated at 500 watts each but are wired in an 8Ω configuration. The reality is that most of the power from the amplifier will be consumed by the resistance of the 8Ω configuration and the speakers will likely only see about 250 watts. So it is important to make sure that your amplifier impedance matches the impedance of your speaker configuration.

Under Powering Your Speakers

When a speaker is underpowered there is the potential of overdriving the amp. This happens when the volume is turned up so loud that the amplifier can no longer produce a constant signal, resulting in audio breakup or distortion known as clipping. Most people think that it’s because the speakers are distorting, but in this case it is the amplifier failing. When this happens the amplifier sends harmful signals (square waves) to the speakers, and these signals can not be reproduced by the speaker resulting in damage to the speakers themselves causing loss of output or even failure. This is especially harmful on smaller, more delicate speakers such as tweeters.

When the amplifier is driven to the point of distortion (peaking or clipping), not only is it harmful to the speakers it also causes damage to the amplifier as well. When an amplifier reaches the point of clipping it can result in permanent damage or failure.

How much power do you need?

Matching the exact RMS Power of your speakers to the RMS Power of your amplifier seems like the logical thing to do, and yes it allows for great sound. If you over-power your speakers by 20%-50% this creates headroom within the amplifier, and will produce a fuller sound when played at all volumes. The additional headroom will enable your amplifier to contend with any sudden spikes in the audio signal. When an under powered amplifier receives an audio spike, it will not have enough power to reproduce the signal, instead it will produce a distorted signal.

The image below is an example of the output volume of an audio signal played at ¾ volume. If you have an amplifier that is rated at 50 Watts RMS (the Red horizontal line), you will notice that there are plenty of spikes in the audio that surpass the 50 watt range of your amp. These spikes will still be audible, but they will most likely be distorted and will cause your amplifier to produce excessive heat when they are reproduced.

If you had an amp that was rated at 75 Watts RMS (the Green horizontal line), you will notice that none of the audio spikes reach the 75 watt range, and the amplifier has plenty of power to reproduce the audio signal clearly without distortion. You will have the same volume without the distortion. The space between the Red and Green lines is what is referred to as Headroom. Headroom is basically how hard you can push your amplifier before it will distort. It is always a good idea to have plenty of Headroom within your system for this exact reason.

Headroom Graph

It is true that your 50 watt speakers may produce some distortion since the amplifier has a 50% higher power rating than the speakers. One way to accommodate for this is to dial the amplifier’s input gain down slightly, as this will allow your amplifier to perform efficiently and not generate too much power for the speakers.

Will a More Powerful Amp Make Your Speakers Louder?

A more powerful amp will give your audio system more headroom, and improve the sound quality of the audio. The more power will let you turn up the music before the amplifier distorts. However if the speakers can not handle the additional power they will distort. With a more powerful amp and speakers that handle the power, you’re speakers will definately be louder.

Wiring: Manufactures recommend wiring specifications in terms of gauge (thickness) and material of wire for their products. Using wiring that is too thin or made of inferior material wire will starve the amp of the power that it needs to perform at its optimum, thus limiting the amplifier’s performance.

Bridging: When 2 channels are combined to create one channel. This process cuts the ohm load in half therefore providing more power to the speaker that the amplifier is powering. This practice is commonly used to power subwoofers on a multi channel amp. For example if you have a 4 channel amp, channels 1 and 2 are used to power your left and right speakers, channels 3 and 4 are bridged to power a subwoofer. Note: Not all amplifiers are capable of bridging.

Features

Audio Filters: Filters are an electronic device that can be found within amplifiers that control what frequencies are sent to your speakers. This is extremely helpful because they allow you to fine tune your amplifier to your speaker selection and your vehicle. Filters are available in both Fixed and Variable. A Fixed Filter is a filter that has only has one setting that is predetermined by the manufacturer. A Variable Filter allows you to adjust the setting of which frequencies are affected by the filter.

Filter Types:

  • High Pass Filter: An electronic filter that allows signals higher than a specified frequency to pass through its circuit, frequencies below the specified frequency are muted.
  • Low Pass Filter: Exactly opposite of the High Pass Filter, this filter allows all frequencies below a specified frequency and all frequencies above the specified frequency are muted.
  • Subsonic Filter: Mutes the ultra low frequencies that are not in audible range, this reduces the workload of both the amplifier and the speakers. Why have your audio components reproduce audio that you cannot hear?

Adjustable Input Level: This function allows you to boost or cut the signal that is sent to your amplifier from your car stereo. This helps you dial-in the input signal strength to your amp to help minimize distortion within your unit.

Adjustable Output Level: This provides control over the signal strength that the amplifier sends to the speakers, to ensure that your speakers are not inadvertently overdriven and protects the amplifier from distorting or overheating.

High Resolution: Because of High Resolution Audio’s ultra-wide frequency response (up to 100 kHz), most standard amplifiers cannot reproduce all of the audio. Some of these tones may never be heard individually but when they are combined with the original audio of a recording, it breathes new life into the recording, offering more depth and ambiance.

Speaker Level Inputs: Enable you to use the speaker outputs from your car stereo to send signals to the amplifier. This is especially helpful when you do not have line level outputs (RCA) on your car receiver.

DSP (Digital Signal Processing): Some amplifier manufacturers offer models that feature onboard DSP. The DSP component allows you the ability to tune your amplifier to your vehicle by means of adjusting the EQ, Signal Delay, and Phase so you can get the best sound out of your vehicle’s audio system.

Amplifier Classes

Although there are many different classes of audio amplifiers, only a handful of amp classes are commonly used in the world of car audio. Without going into a lengthy explanation on the physics of how each amp class works, it is much easier to understand the pros and cons of each amp class.

Listed below are the most prevalent amplifier classes used within the industry.

Class A: An analog amplifier. Mainly used in higher end car audio installs.

Pros:

  • Extremely accurate output
  • No crossover distortion
  • Very good high-frequency response

Cons:

  • Large in size
  • Generates a great deal of heat
  • Very inefficient
  • Heavy
  • Expensive

Class B: An analog amplifier that uses a push/pull method for reproducing audio. Not commonly found in car audio.

Pros:

  • Decent quality audio output
  • More efficient than Class A amps

Cons:

  • Crossover distortion
  • Generates heat
  • Very inefficient
  • Expensive

Class A/B: A hybrid between Class A and B amplifiers, this type utilizes the best attributes of the Class A and B amplifiers to create an amplified signal without the drawback of either class.

Pros:

  • Acceptable crossover distortion levels
  • More efficient than Class A amps

Cons:

  • Generates less heat than Class A amplifiers
  • Expensive

Class D: Digital amplifier. The most common amplification found in car audio. This type of amplifier generates a fair amount of crossover distortion. In order to minimize the effect of the distortion, the audio quality may suffer, depending on the make and model of the amplifier.

Pros:

  • Generates very little heat
  • Far more efficient than Class A amps
  • Smaller size
  • Inexpensive

Cons:

  • Crossover distortion
  • Sound quality

Amplifiers come in many configurations. The easiest way to find out what you need is to think about what you are wanting out of your vehicle’s audio system. Once you have determined your audio needs, you can simply use our Filter Menu (located on the left hand side on product landing pages on a desktop or the Filter Button on mobile) to narrow down your search. If you need additional assistance stop by your local Car Toys store. Our product experts and professional installers are there to assist you with all of your car entertainment needs.