How to Install an Amp in a Car With Factory Radio in 10 Steps

An amplifier upgrades the listening experience for you and your passengers in the car. It improves the clarity of your speaker, prevents distortion, and reduces road noise. If you want to add an amp to factory radio, this tutorial is for you.

On the back of your amplifier, you will find two RCA input jacks, three power inputs (they are called battery, remote, and ground), and two output jacks. Your job is to connect your car stereo to the amp’s five input jacks, then connect its two output jacks to the subwoofer.

You only need an amp installation kit, a line output converter, wires, and some tools. In this article, we will provide an in-depth tutorial on how to install an amp in a car with factory radio. Dive in!

What You Will Need


1. An amplifier installation kit

A kit includes:

  • One red power cable
  • One black ground cable
  • One blue amp turn-on wire (also called remote wire)
  • One fuse holder
  • Crimp connectors for wiring

If your kit doesn’t have electrical butt connectors, you’ll need to purchase them separately.

2. RCA signal cables

For mono and two-channel amplifiers, you need one set of RCA signal cables. For four-channel amplifiers, you need two sets of RCA signal cables. A set comes with two audio jacks on each end.

3. A line output converter

A car stereo has up to nine different wires. You don’t want to run each of them to the amplifier. A line output converter helps convert all these wires to one remote wire and one RCA signal cable so you can install the amp to factory radio easily.

4. Speaker wire

When you finish installing the amplifier, you will connect it with the subwoofers. So, prepare three to four feet of speaker wire.

5. A car wiring diagram

Without a wiring diagram, you won’t know how to connect the amp to factory radio. You can find your car model’s wiring diagram online or in factory manuals.

6. Tools

The tools you need include:

  • A screwdriver
  • A soft panel removal tool
  • A utility knife
  • A drill gun and bits
  • A socket and ratchet set
  • A wire stripper
  • A wire crimper
  • Electrical tape

Steps to Install an Amp in a Car With Factory Audio


Step 1. Prepare for the installation


You should disconnect the negative terminal of the car’s battery to prevent a short circuit. You should also decide where to place your amplifier. We recommend having it in your car trunk.

If you choose to place the amp like so, you will need to run the ground, remote, and RCA cables from the head unit to the back of your car.

Step 2. Remove the dash and panels

Start by disassembling the dash using the soft panel removal tool and screwdriver. You can find your car model’s dash disassembly online and follow it to avoid damaging your dash. When the dash is off, you will see your car stereo.

Then, disassemble the areas that the cables will run through. Those include kick panels, door scuff plates, lower trim panels, upper trim panels, and seat belt cover anchors on both sides. Don’t apply too much force as you might pull panels that have hidden screws and break the piece.

Step 3. Install the line output converter


Now, on your line output converter, you’ll find seven input wires, one blue output wire, and two audio jacks.

Grab the blue amp turn-on wire (remote wire) in your amp installation kit and connect it to the converter’s blue output wire. Follow these steps:

  • Strip ½ inch of insulation on each wire
  • Twist the metal core together
  • Secure them with one electrical butt connector.
  • Wrap electrical tape around to ensure the wires won’t move.

On the back of your car’s stereo, you will see seven speaker wires. Use your wiring diagram to locate the compatible wires and connect them with the converter’s seven input wires one by one.

Then, plug the RCA cables into the converter. The red jack goes into the red input and the black jack goes into the black input. When you have connected everything, leave the stereo out just in case you need to correct the wiring later.

Step 4. Run the power cable

Your car’s battery supplies power for the amplifier. So, you need to run the power cable from the battery in the engine bay to the amp in the trunk. Run it on the same side of the battery to make it short and clean.

  • Drill a hole in the car firewall to pass the cable through.
  • Run the power cable from the car’s battery through the hole.

Don’t connect it with anything yet, as you need to run it along the remote wire. For now, leave it at the kick panel and secure the other end in the engine compartment with a zip tie.

Step 5. Run the remote wire

Run the remote wire from the line output converter to the firewall hole that holds the power cable. After that, hold them together and run them to the amp.

Stay away from the gas and brake pedals, run the wires at a slant across the floor. Then, run them through the sill plate, middle pillar, rear sill plate, and the back seat, and pull the wires to the trunk. You can use zip ties along the way to keep the wires in place.

Step 6. Run the RCA signal cable

Similarly, run the RCA cable signal from the output line converter to the trunk on the other side of the car. Don’t let the cable get in the way of the passenger. Instead, run it diagonally across the floor, through the sill plate, middle pillar, rear sill plate, and the back seats, and pull the cable to the trunk.

We don’t recommend running the RCA cable on the same side as the power and remote wires. Though it saves you some time, the cables will overlap one another and cause sound interference.

Step 7. Wire the amp


Once the head unit is set up and all the wires are in their place, you can move to wire the amp.

Strip back ½ inch of the plastic insulation at the end of the remote wire and power cable. After that, connect them to the amp. The red power wire goes into the 12-volt input. The blue remote wire goes into the turn-on input (REM). The red and black RCA jacks go into the red and black input.

To hook up amp to stock radio, you must also connect the speaker wire from the amplifier’s speaker output to the subwoofer.

Step 8. Set up the ground cable

  • Strip back ½ inch of the insulation on one end of the cable.
  • Insert it into the ground input (GND) on the amplifier.
  • Find a nearby bolt and scrape its paint off.
  • Use a crimp ring to connect the other end of the cable to the bolt.

By connecting the ground cable to the car’s chassis, you completed a constant power supply circuit to install amplifier to stock radio.

Step 9. Install the fuse holder

The fuse holder helps to cut the power in the event of an overcurrent. This is the last thing you need to set up to install aftermarket amp to factory stereo. Go to the engine bay and carry out these steps:

  • Cut ½ inch of insulation on the power cable end that you zip-tied in the engine bay.
  • Slide one end of the fuse holder inside and tighten the screw on top of the cable.
  • Prepare a short piece of power cable and strip back ½ inch of insulation.
  • Insert the other end of the fuse holder into that piece.
  • Twist the two ends of the fuse holder together to connect two pieces of power cable.

Finally, connect the short cable to the positive terminal of the battery by a crimp ring and you have succeeded in adding an amp to factory stereo.

Step 10. Finish up by reassembling the dash and panels


On many amplifiers, you need to set up the filters and gains to prevent distortion. So, do that if necessary. Once you have finished, reassemble the dash and panels and secure them properly.

This video will help you learn the whole process:


That’s how to install an amp in a car with factory radio in ten steps. When you have the materials and tools handy, following this tutorial will be easy. Don’t forget to save our article so you can refer back to it as you go. When your factory radio is added an amp, you’ll never want to go back to regular car stereos.

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