Car Amplifiers: Do You Really Need Them?

Car audio amplifier essentials: channels, power, and clarity

Amplifiers are often associated with high-performance car audio. However, every car audio system requires an amplifier, whether it's a weak, built-in feature or a separate, high-powered unit. In fact, a car stereo wouldn't work without one. Most car audio systems and simple upgrades don't include a separate amplifier, although many include a dedicated amplifier to drive a subwoofer.

What Audio Amplifiers Do

In both home and car audio systems, an amplifier strengthens a weak audio signal. When the signal that goes into the amplifier is too weak to drive speakers, the signal that comes out can get the job done. The power of an amp dictates how loud and distortion-free the sound is.

Do You Really Need a Car Audio Amp?

Here are a few benefits of including a separate amplifier in your car audio system:

  • Louder sound without distortion: A good amplifier lets you increase volume without also increasing distortion. If you experience distortion at your desired volume, you probably need an amplifier.
  • To power a subwoofer: When you add a subwoofer to a car audio system, you almost always need to add an amplifier at the same time. If your car radio doesn't have connections that are specifically designed for a subwoofer, add a subwoofer amp.
  • To get the most out of your new speakers: You can add new speakers to a factory car audio system to improve its sound, but a new head unit and a separate amplifier give you more speaker options.

If you don't mind a little distortion, and you have no desire to crank your head unit to 11, you can probably skip the amp and focus on the head unit and speakers. Some head units have enough power to provide relatively distortion-free sound, and adding a high-pass crossover can help clear things up.

Another factor to consider is whether the head unit includes preamp outputs. These outputs bypass the built-in amplifier and send a clear signal to an external amplifier.

If your head unit doesn't have preamp outputs, you'll need an amp with speaker-level inputs. The other option is to use a speaker to line level converter. While both of these methods tend to introduce noise or distortion, the only other option is to buy a new head unit.


Although upgrading a head unit prior to adding an amplifier costs more, it provides the best results. A decent head unit makes finding the right car amp easier.

Head units that contain powerful amps are more expensive than basic models. Often, the more economical choice is to pair a head unit that features preamp outputs with a dedicated amp.

Channels and Other Amplifier Features

One main differentiating factor between amps is how many channels they have. They are available in multiple configurations from mono to six channels, each of which is best suited to different speaker setups.

At least one channel is needed for each speaker, but you can use more than one amp in a single car audio system. For example, a four-channel amp can power four coaxial speakers, and a separate mono amp can be used for a subwoofer.

Each amp must be matched to the system that it's going to power. Some amps have low-pass or high-pass filters built in, which make them ideal for powering woofers or tweeters. Other amps have variable filters, bass boost, and other features.

The Importance of Power in Car Audio Amplifiers

The power of an amp refers to the wattage that it can send to the speakers. Because the point of an amplifier is to increase the audio signal strength, the power of an amp is an important consideration.

The key value here is the RMS, but there is no specific number to look for. The RMS of an amp should be matched to the power handling of the speakers, which is different in every car audio system.

An RMS somewhere between 75 percent and 150 percent of the power that the speakers can handle is best, and overpowering the speakers a little is better than underpowering them.

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