Buying an amplifier for a car audio system can be a daunting task. Whether you’re a car audio enthusiast or just a casual driver looking to improve the quality of your car audio system, it can be a challenge to look for and select the perfect amplifier.

That’s why in this blog, we’ve put together this guide to help you find out what type of amplifier you need for your new system. Remember – you should either choose an amplifier first and build your system around it, or you choose the other components first and choose an amplifier (or amplifiers) to power the components. This complete car amplifier buying guide assumes you have an idea of what type of system you want without any idea about the amplifier.

Knowing Your Amplifier Class

An amplifier increases the power signal it’s being fed from the head unit. When sound is being played, it boosts the amplitude (size) of its signal headed toward the speakers from the stereo. The highs stay crisp, the lows are bumpin’ and the melodies flow.

Every amplifier follows the same fundamental operating rules and serves the same purpose. That does not imply, however, that all car amplifier classes are created equal. As opposed to others, some amplifiers are better suited for particular uses.

Amplifiers are engineered to convert these electrical signals by a few different methods called “classes.” The most common amplifier classes are A, B, A/B, and D:

  • Class A: 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: a little more efficient than Class A and has the potential to suffer from “crossover distortion” as the circuits push-n-pull between one another. 
  • Class A/B: The most common amplifier used in Hi-Fi systems. Combines the functionality of A with the efficiency of B.
  • Class D: 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.

Selecting a Channel Configuration

All amplifiers are designed to output power into different “channels”. This helps pair the amplifier to the application it’s being used in. The most common amplifiers are 2-channel, 4-channel, and monoblock. Now, just because an amplifier is branded as a “2-channel” doesn’t mean it’s only capable of powering 2 speakers. In theory, it’s possible to have as many speakers as you want to be paired with a 2-channel amp, it will just change the impedance (ohms) and change how the power is distributed between the speakers. Even though it’s possible to wire many additional speakers, it’s most common to use a 4-channel amplifier for 4 speakers, a 2-channel for 2 speakers, and so on.

Here’s a list that helps identify each different amplifier channel configuration and more information about each one:

Monoblock Amplifier

Belva BXA15001

  • Mono (one channel, no Left/Right differentiation)
  • High-powered car amplifier
  • Not full-range since subwoofers do not play higher frequencies
  • Usually used to power one or more subwoofers
  • Commonly has Class D circuitry, however, can also have Class A/B as well

Monoblock amplifiers are designed primarily for subwoofers. Subwoofers require a lot more power than standard speakers, and the signal does not need to be as clean as the signal going to a full-range amplifier. Bass doesn’t need to be processed as much for high-quality sound, as a really nice full-range amplifier does. Monoblocks are also not usually full-range capable because higher frequencies are not played by subwoofers. Having these amplifiers capable of playing high frequencies would be a huge waste of efficiency. Because subwoofers require much more power than smaller tweeters or door speakers, monoblock amps are designed for maximum efficiency and power output first.

If what you’re looking for is a monoblock amplifier, here’s a list of our best-selling monoblock amps at Sonic Electronix.

2-Channel Amplifier

Alpine BBX-T600

  • Stereo
  • Full-range
  • Bridgeable
  • Can be used to power one set of speakers (2 total speakers)
  • Most commonly used to power a subwoofer, or multiple subwoofers
  • Usually has Class A/B Circuitry, but can also have full-range Class D as well

Perhaps one of the most popular selections, 2-channel amplifiers are great for multiple purposes. Two-channel amplifiers output dedicated power to two separate channels, great for powering one set of car speakers (2 total speakers). The two channels can also be combined, or bridged together to provide more output to one dedicated channel, and is commonly done to power a subwoofer or subwoofers. 2-Channel amplifiers are stereo, meaning they have a Left and Right output. This is important for staging and tuning. These amplifiers are capable of playing what is considered the full spectrum of sound that humans can hear, usually around 20-20,000 Hz.

If what you’re looking for is a 2-channel amplifier, here’s a list of our best-selling 2-channel amps at Sonic Electronix.

3-Channel Amplifier

JL Audio XD500/3v2

  • Hybrid Amplifier
  • Front 2-channels are stereo/1 channel is mono
  • Basically a 2-channel amp and a monoblock amp combined
  • Most commonly allows an entire truck system to be powered from one amplifier (2 speakers, 1 or more subwofer)

3-Channel amplifiers are a smaller version of a 5-channel. They’re basically a 2-channel amplifier and a monoblock combined. They’re most commonly used to power an entire audio system in a 2-door truck, or other small vehicles similar to this. You’ll also find 3-channel amps used to power just the front speakers and a subwoofer in a budget system.

4-Channel Amplifier


  • Stereo
  • Full-Range
  • Bridgeable (most of the time)
  • Usually used to power two sets of speakers (4 total speakers)
  • Also able to be used in other configurations, however this is not as common
  • Usually has Class A/B Circuitry, but can also have full-range Class D as well

Another popular option, 4-channel amplifiers, are commonly used to power an entire set of door speakers (4 total speakers). 4-Channel amplifiers are also bridgeable, allowing for a ton of configurations, but the most popular application we find these amplifiers in is powering door speakers.

If what you’re looking for is a 4-channel amplifier, here’s a list of our best-selling 4-channel amps at Sonic Electronix.

5-Channel Amplifier

Rockford Fosgate R2-750X5

  • Stereo
  • Hybrid amplifier
  • Front 4-channels are stereo/1 channel is mono
  • Basically a 4-channel amp and a monoblock amp combined
  • Allows an entire system to be powered from one amplifier (4 speakers, 1 or more subwoofer)
  • Good for those who don’t want multiple amplifiers powering their entire system

5-Channel amplifiers are basically a mixture of a 4-channel amplifier and a monoblock amplifier, built into the same chassis. This helps eliminate the need for multiple amplifiers and elaborate wiring scenarios. These amplifiers are a great, simple solution for those looking to power 4 speakers and a subwoofer. They’re a bit more difficult to use for high-powered audio applications since 5-channels are usually only capable of running around 600-1000W RMS. This amount of power is perfect for mid-tier audio systems though.

If what you’re looking for is a 5-channel amplifier, here’s a list of our best-selling 5-channel amps at Sonic Electronix.

Multi-Channel Amplifier

Cerwin-Vega H900.6D

  • Stereo
  • Full-range
  • Similar to a 4-channel amplifier, but with 2 or more extra channels
  • Allows powering of a center channel, or two additional sets of speakers
  • Usually for specific audiophile applications

Multi-channel amplifiers are usually reserved for audio enthusiasts or those with specific audio applications in mind. These amplifiers are most commonly used in vans, SUVs, and boats where you may require more than the traditional 4-speaker setup. They can be used in a lot of installations, but usually, they’re bought with a certain application in mind.

Determining Power Requirements

Trying to match up your system’s power requirements with an amplifier can look confusing, but really it’s easier than it seems. The first thing to always remember is to only look at RMS power. Looking at peak or max power without a deeper understanding of it, will only confuse you. Secondly, impedance (or ohms) is a way to measure resistance. All speakers have an ohm rating, or impedance that tells the amplifier how much power to output. Lower impedance means more wattage from the amplifier. At 4 ohms an amplifier will output less power than at 2 ohms; however, an amplifier is more comfortable running at higher impedance and will tend to run cooler. For example, an amplifier at 4 ohms may put out 75 watts RMS, and at 2 ohms this same amplifier will output 100 watts RMS. Finally, you’re going to want to match up the impedance and RMS wattage of the speaker and amplifier. For example, if the manufacturer specifies that each speaker will require 100 watts RMS at 4 ohms, you will want to find an amp that pushes between 70-130 watts RMS at 4 ohms.

For more information regarding impedance, check out this video on matching subwoofers and amplifiers:

You may also want to check out our subwoofer wiring diagrams to show you the proper, exact way of connecting your subs to your amplifier.

Although you will get sound from a speaker even if you’re powering it with less than 70% of the rated RMS power, it’s usually not advised. When underpowering a speaker or subwoofer there’s a problem you’ll run into called “clipping”. This occurs when the amplifier tries to push more power to the subwoofer or speaker than the amplifier is safely capable of reproducing. For more on clipping, check out this video.

Determine if Auxiliary Battery is Required

Batteries are underused in car audio, when in reality they should be overestimated and overused. It’s understandable, considering that adding an additional battery is a bit of an investment to an already expensive complete system build, however, the investment can be put to exceptional use in moderate and higher-powered systems. Personally, I agree with the rule of thumb that systems running over 1000 watts of total RMS power should ALWAYS have at least an upgraded starting battery. An auxiliary battery should also be highly considered in these types of systems. The reason for this is, car audio systems are very demanding when it comes to using power. Your vehicle has a battery used to start your car, but also powers things like your head unit, air conditioner, power windows, illumination on the dash, and, perhaps most importantly, headlights.

A common symptom you’ll see when adding a higher-powered car audio system (600W RMS and up) is that when the bass hits, you’ll see your headlights dimming. This is because bass is very demanding, and every time it’s hitting it’s pulling a ton of voltage from your battery. In order to combat this, I’d personally recommend any system over 600 watts of RMS power (or fuses that add up to 60 amps or more) should highly consider either upgrading their starting battery to one more capable of keeping up with their system, or adding an auxiliary battery.

Determining The Right Wire Gauge

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Now, you’ve picked out your amplifier, and you’ve picked out the speakers and subwoofer(s). You’re reading to get this system ordered and installed. Hold up. One last final thing to mention is wiring. Now, we’ve stressed the differences between Copper Clad Aluminum (CCA) and Oxygen-Free Copper (OFC) wiring before in some of our videos and blogs. This is important to consider, but mainly we’re going to assume you went with OFC and are curious about the gauge of wire to choose.

The fuses on your amplifier (if your amplifier has them, lately more manufacturers have been opting out of external MIDI fuses and relying on your main fuse near the battery to protect your amplifier) are a good place to start to determine what wire gauge to choose. The reason for looking at fuses instead of rated power, is that power ratings with amplifiers can be very misleading. Reliable manufacturers in the industry who follow CEA-compliant power ratings are much easier to determine wire gauge for than manufacturers who just list peak power or over-inflate their RMS power ratings.

Looking at the total RMS power for your amplifier(s) is the way to determine the main run from your battery to your amplifier area. Another factor to consider is the length of the wire run. If you have your amplifiers under your front seat, you may be able to get away with a small gauge then if you’re running it to a trunk. Consider the RMS power, the length of the run, and the quality of the wire that you’re choosing to find out if you’re using a large enough wire to allow for proper system requirements.

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.