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How to Install an Amp in a Car With Factory Radio in 8 Steps?

Writen by Edwin Jones

Fact checked by Andrew Wright

how to install an amp in a car with factory radio

Adding an amp to the factory stereo is a great solution to enhance the driver’s listening experience. However, if you do not have technical knowledge of this process, this project may be challenging or impossible for you. Through this article, we will explain how to install an amp in a car with factory radio.

How to Choose Amp for the Car Factory Radio

The number of channels is one of the standout differentiators of amplifiers. In most cases, the channel number of an amplifier is somewhere between one and six. For the best performance of your speakers, you need to make sure the amplifier you choose is compatible with your speaker system.

You typically need at least one channel per speaker. That means if you will install three coaxial speakers, it is best to choose a 3-channel amplifier. On the other hand, it is essential to install a 1-channel amplifier to power the subwoofer.

In short, you need to hook up an amp to a factory stereo if you want a perfect sound system that can provide excellent performance.

Complete Guide to Install an Amp in a Car With Factory Radio

The necessary tools

Before you proceed to connect amp to factory radio, it is essential to prepare the necessary tools; These include:

  • Speaker wire
  • Amp installation kit
  • Wirecutter/stripper
  • Universal back straps
  • Electrical tape
  • Torx driver
  • Flashlight
  • A plastic bowl (to hold screws)
  • Bojo trim panel tools
  • A clean cloth

Step By Step Guide

Step 1: Prepare suitable materials


Before buying an amplifier, consider a few of the most critical factors. In general, it is best to choose a model of a well-known brand.

Besides buying an amplifier, buying the speaker-level inputs/terminals is also necessary. Also, you need an amp installation kit input that comes from a trusted brand.

After you have all materials needed for the project, arrange them near you so that you can easily reach them.

Step 2: Take safety precautions

Of course, your safety comes first. So, the car battery negative terminal needs to be disconnected before you do anything.

Step 3: Put the amp in the car’s trunk


According to experts, the trunk is the safest place to place the alternator. You can put it on the sidewall, floor, or anywhere in your car’s trunk.

Step 4: Prep the ground and power wires

A standard amp installation kit should have all the wires needed for this project, including the power wire (red). So let’s start with pulling this wire and connecting it to the battery’s positive terminal through your car’s cabin; Then extend it to where you put the amp.

Next, you need to do the installation with the ground wire. Find a bolt or nut on the chassis (nearby the amp) and attach this wire to it. You should remove any material that could prevent this wire from being attached firmly to the chassis, such as paint or dirt; You should use a screwdriver, the Bojo trim panel tools, or a paint scraper to do this.

Step 5: Determine the rear speaker wires

Be careful when determining the wires which run through your speakers; Use a stripper or wire cutter to open up the negative and positive wires.

Run a speaker line to each stripped wire and apply electrical tape to secure them. Next, these wires need to be connected to the speaker-level terminals on your amp; Each wire needs to be appropriately connected.

You must handle this process with good attention to detail until all speaker wires are correctly connected to the speaker-level inputs.

Step 6: Connect the wire and speaker output


After completing the above step, linking the speaker wires to the amplifier’s speaker outputs and connecting them to the subwoofer or speakers; Again, these wires need to be correctly connected.

Step 7: Link ground and power wires to your amplifier

At this step, all you need to do is connect ground and power wires to the appropriate inputs on your amplifier. All connections should be firmly secured.

Step 8: Run test your audio system

Last but not least, reconnect your battery terminal and check whether the connection is successful.

If the amplifier does not operate normally or gives the desired results, disconnect your battery to check the wires.

Watch the following video to better understand how to connect amp to factory radio.

Intended time and cost to install an amp

Once you know the process and have the needed tools, it will take you one to four hours to complete this project.

Overall, the time it takes to complete this project depends significantly on your experience. If you are not sure how to connect the amp to the factory radio, you can always call an expert.

Estimated cost

  • Professional
  • If you want to complete this project by hiring a professional, you must spend $120 to $140.
  • DIY
  • Amplifiers usually do not come with installation wiring. Therefore, don’t forget to invest in an amplifier wiring kit when you buy an amplifier. This kit has the necessary wiring (ground and power wires) and fuses. It is possible to buy a high-quality amp wiring kit for under $50.
  • The price of a 1-channel amplifier usually ranges from 80 dollars to 300 dollars. If you are looking for a multi-channel amp, choose a top-quality model that ranges from 100 to 500 dollars.

Read more: Costs to install a car radio.

Why Should You Add Amplifier to Factory Car Stereo


When you apply a separate amp in your aftermarket audio system, you will get many benefits; These include:

  • The power of the subwoofer is significantly increased
  • By installing a high-quality amplifier, you will get louder sound without distortion. As a result, the clarity of the sound is not affected when you increase the volume.
  • Power up your new/upgraded speakers
  • If you are looking to upgrade the speakers, installing a new amplifier is essential. It will help your new speakers reach their full potential.
  • In fact, your new speakers are unlikely to achieve optimal performance with the built-in amplifier.
  • Improve the power of the subwoofer
  • If you plan to connect your sound system to a subwoofer, consider installing an amplifier. The purpose of this is to deliver outstanding performance to the subwoofer.

Frequently Asked Questions

Should I invest in an aftermarket radio?

It can be pretty expensive to buy a new radio before installing an amplifier. However, you will get a lot of benefits out of it. For example, you can easily choose the perfect amplifier for the sound system and the speaker designs you want.

Is the power rating in an audio amplifier critical?

The short answer is yes. An amplifier’s power indicates the power that the amplifier can send to the audio speakers. Therefore, before buying an amplifier, it is essential to focus on the output power.

Can you use a subwoofer without an amp?

In fact, subwoofers can boost bass frequencies, creating a deep and powerful sound. Most subwoofers are paired with an amp to boost the sound. However, you can still add a subwoofer without an amplifier.

How do I check an amp to see if it works?

One of the easiest ways is touching the power cord from the amp to the battery’s positive terminal and the ground wire to the battery’s negative terminal. Then, if the power light comes on, you can be sure that the amplifier has a good board.

Do you need an amp for my aftermarket radio?

You do not need to install an amplifier if you do not care about the sound quality or are happy with the existing system. However, the addition of an amplifier is necessary when you want to improve your sound quality.


All in all, adding an amp to factory stereo is a great solution to improve the performance of your stereo/radio (aftermarket or factory). Just follow our guide; you can install aftermarket amp to factory stereo/radio without any problem. So are you ready to enjoy powerful sound in your car for a long time?

Also, if you find this guide on how to install an amp in a car with factory radio helpful, you can share it with people that need some help. Thank you!

Read more: Steps to install a radio without a wiring harness adapter.

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