Most of sound systems in cars are built with an amplifier, but many of them are not external but located in head unit. This is one of the most common reasons for distortion when you crank up the volume. If you are looking for the best car amplifier or upgrade an existing one, there are a couple of different factors that you need to take into consideration, including:

  • Number of channels
  • Power
  • System compatibility

What is the suitable number of channels?

These days, car amplifiers are available in the market with various configurations. And the right channel numbers would depend on how many speakers there are in your car’s sound system. Generally speaking, you might need 1 channel for every speaker that you need to amplify. If you want to add a subwoofer into the existing system, then the best option would be an amplifier with a single channel. There is also a mono amplifier with “D class” rating that is designed specifically for putting off heat and using less power during the process of amplifying subwoofers.

A unit with 2, 4, or 6 channels is more versatile. For example, a 2-channel amplifier could be applied to power 2 woofers, 2 coaxial speakers, or you could run a single sub by bridging it. If you only want to install a subwoofer and give more power to the rear full-range speakers, then the most suitable choice would be a 4-channel amplifier. In that situation, you could run each full-range speaker off its channel and then bridge the others to get power for the sub.

On the other hand, you would power all of 4 coaxial speakers off the similar amplifier and then set up a separate mono amplifier for the subwoofer.

Component systems could be more complex, and you might end up calling for more than a single amplifier, external crossover, and other parts.

Do not skimp on power

If you need to get the best performance out of the stereo on your car, it is important that you do not underpower the speakers. That is the reason why a lot of drivers pick out speaker first and then find a suitable amp that would power them enough. If you are just contacting with the factory speakers, you would still need to determine the RMS value and then go for an amplifier that is capable of putting out from 75 to 150% of the number.

Also, power would be a concern when you are planning to operate a sub off the similar amplifier, which you are using for the speakers. Bridging 2 channels of an amplifier with multi-channel might give enough amount of power to operate a sub, but it is not suitable in all cases. If the amplifier could not match the specific power needs of your subwoofer, then it is better to look for a separate mono amplifier, which is capable of performing the job correctly.

Amplifier compatibility and head unit

If you are building an audio system for your car from the scratch, then there is no question about that: choose a head unit with preamp output and an amp with line level input.

Most head units in the factory and a lot of aftermarket device do not have preamp output. If you are working with the current unit which belongs to this category, then you will need to search for an amplifier with speaker level input. This would still lead to better sound quality than you would get without an external amplifier, and it would also keep you from messing around with additional adapters or wiring.

My name is John Henry, founder of – blog about automotive industry. With 20 years experience in repairing, troubleshooting and maintaining thousands of cars, I create this blog to share my knowledge as well as skills with car owners all around the world. Hope you like it.

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