Car Amplifiers Buying Guide

If you want to pump up the volume on your car stereo, you may want to keep things in check with an external amplifier. An external amplifier will allow the sound waves to reach your ears clearly from the speakers, so when you are on the move, your music can still sound great.

What is a car amplifier?

Car amplifiers are used to increase the frequency of low power audio signals so that a cleaner sound may pass through the speakers. The amplifier can convert a low-power signal from a pre-amplifier into a high-power signal needed to drive a loudspeaker ; this allows for clear sound quality at any and all volumes.

Top Rated Car Amplifiers

Mono Channel

Dual Channel

Multi Channel


Key Features

These are the key features of an amplifier as described by

Built-in CrossoversOften used to keep high-frequencies from reaching a subwoofer. A low-pass crossover allows only low frequencies to be amplified, and a high-pass crossover allows only high frequencies to be amplified. It keeps low bass away from small speakers, so they can play more efficiently.
Bridged PowerBridging a car amplifier combines the power output of two channels into one channel, and allows the car amplifier to drive one speaker with more power than the amp could produce for two speakers. Because of this high power output, bridging is the best way to drive a single subwoofer.  If the amp is bridgeable, the owner's manual will have directions that tell you how to do so.

Also, keep in mind that most car amplifiers need to see a 4-ohm load when bridged to mono operation. If you want to bridge your amp, you should use one 4-ohm speaker or, if you prefer multiple woofers, wire two 8-ohm speakers in parallel. (Consult your manual before operating your car amp in bridged mode.)
Discrete Output DevicesThere are 2-3 basic types of output devices found on car audio amplifiers: 1) integrated circuits, 2) bipolar transistors, or MOSFETs. An integrated circuit (or IC) is found only on relatively low-wattage (20 watts RMS per channel or less) amplifiers called "bridged transformerless" amps. An IC cannot pass enough current to work on a more powerful amp and is not considered a discrete output device. Bipolar transistors and MOSFETs are found on the output stages of high powered amplifiers. They are fast enough and can handle enough current to send wattage greater than 20 watts per channel to your speakers. Both of these types of transistors are considered discrete output devices. Usually there are two per channel, but some amps feature as many as four.
Mono Amplifier 
Mono (or monaural) car amplifiers are single channel amps, well-suited for low-frequency applications. Mono car amplifiers are stable to 2-ohms, so you can connect them safely to two 4-ohm woofers wired in parallel.
MOSFET  (Metal Oxide Semiconductor Field Effect Transistor)
A type of large output transistor used in the final stages of many power amplifiers, and commonly found in most car amplifiers today. Mosfet transistors are most often discrete devices, used with smaller driver transistors and other devices to convert a small signal to a large one. They are highly stable and efficient, compared to the bipolar types that preceded them.
OhmThe measurement of electrical resistance and system impedance. It is a measure of the degree to which electrons are limited in both velocity and quantity in passing through a circuit. In Impedance measurements, this takes into account the mechanical resistance inherent in the motion of transducers. The standard is usually 4 ohms for car audio.
ParametricA type of equalization that permits the centre frequency, the filter shape, and the amplitude of each band to be varied. This gives you extremely precise control over the tonal balance in your vehicle. (More versatile than graphic equalizers)
Preamp output
This is the first stage of amplification in which the amplitude of a very low-level audio signal is increased. The first stage of amplification in which the amplitude of a very low-level audio signal is increased.
RMS Power
The higher the RMS figure, the louder and cleaner your music sounds. The RMS rating is the maximum the amplifier can put out all day long without distorting. The RMS rating is very important.
Peak Power
The peak power rating tells you the maximum wattage a car amplifier can deliver as a brief burst.  The RMS rating is more important.
Signal-to-Noise Ratio
A measurement of noise level in a device compared to the level of the signal. Higher numbers signify a greater difference, which is better.
Speaker Input 
Speaker inputs let you connect an amp to a receiver that lacks RCA preamp outputs.
Total Harmonic Distortion (THD)
The THD is usually expressed in dB. The ratio of (a) the sum of the powers of all harmonic frequencies above the fundamental frequency to (b) the power of the fundamental frequency.
Tri-Way Output
A Car Amplifier setup that powers a pair of stereo speakers and one subwoofer simultaneously from the outputs of a single 2-channel amplifier.

How to Buy an Amplifier

Things to consider:

  • The number of channels listed on an amplifier indicates the number of speakers that it will power; if you wish to power more than one speaker--or even if you don't--it is smart to get an amplifier with numerous channels. Any additional components for the speakers--such as subwoofers --will require their own amplifiers. 
  • Choose an amplifier with crossovers that have easy to use controls. Some amplifiers have inset controls that must be adjusted wth a screwdriver--this can obviously be a pain in the arse.
  • Soft-start circuitry eliminates the thumps and thuds that can be annoying and potentially damaging to car speakers.
  • Depending on your application, the number of speaker-level and line-level outputs and inputs need to be considered. Make sure you have enough for the set-up you are currently installing, while leaving room for at least one future upgrade.
  • Amplifiers generate a significant amount of heat that affects their efficiency. Numerous methods of dissipating this heat are used--everything from cooling fans  to liquid coolant systems.

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