How to Hook Up Amp to Factory Radio in 9 Steps

If you want to upgrade the sound system in your car but keep the factory radio, adding an amp is a great option. Amplifiers boost the power going to your speakers, allowing them to play louder and sound better. Hooking up an amp to your factory radio is possible in most vehicles with some basic wiring work. Follow this guide to learn how to hook up amp to factory radio in your car.

What You Need

• Amplifier
• Wiring kit
• RCA cables
• Speaker wire
• Crimping tool
• Wire stripper
• Volt meter

Step 1 – Turn off the Power and Remove the Radio

First, make sure the battery is disconnected in your vehicle. This prevents any shorts or shocks while wiring. Then, remove your factory radio from the dash. In most vehicles, this involves unscrewing the trim around the radio and sliding the radio out. Be careful when removing trim pieces to avoid breaking tabs or clips. Set the radio aside in a safe place.

Step 2 – Run the Power Wire

The next step is running a power wire from your amp location to the battery. Use an amplifier wiring kit that includes the power wire you need. Start by running the wire under the interior trim from the back of the vehicle to the firewall. Use grommets when passing through the firewall to protect the wire. Run the wire under the carpet or along the frame rail to the battery. The power wire connects directly to the positive (+) battery terminal.

Step 3 – Connect the Ground Wire

You also need to connect the ground wire from your amp wiring kit. Run this wire under the trim just as you did the power wire. You can ground the wire to any metal surface that has been cleaned of paint and debris. Common grounding points are seat bolts, seat belt bolts, or the chassis itself. Use a crimp connector to secure the ground wire.

Step 4 – Install Fuse Holder

The amp wiring kit will come with an in-line fuse holder. This provides overcurrent protection in the event of a short. Install this fuse holder within 18 inches of the battery connection. Make sure it is secured neatly out of the way using zip ties. Insert the included fuse into the holder.

Step 5 – Mount the Amplifier

With power and ground connections made, you can now mount your amplifier. Typical amp mounting locations include under seats, in the trunk, or behind interior trim panels. Use screws or strong adhesive to secure the amp. Make sure it is somewhere it will stay dry and get proper airflow. Run all of your wiring neatly to the amp mounting location.

Step 6 – Connect the Remote Turn-on Wire

The remote turn-on wire tells the amp when to turn on and off based on whether the radio is on. This wire needs to connect to an accessory power source that provides 12V when the radio is on. At the radio harness, locate the accessory wire and use a splice connector to tap into it with your remote turn-on wire. This makes the amp turn on whenever the radio turns on.

Step 7 – Connect RCA Cables

With power, ground, and remote connections made, you can move on to the audio signal connections. RCA cables carry the amplified signal from the head unit to the amplifier. Plug the RCA cables into the matching outputs on the back of the factory radio. Then route the cables to your amp and plug them into the inputs. Make sure to connect the left and right channels properly.

Step 8 – Connect Speaker Wires

Now you need to run new speaker wires from the amp outputs to each speaker location. The amp will provide speaker-level inputs that connect to your speakers. Use good quality copper speaker wire, making sure to maintain proper polarity. Connect the positive wires from the amp to the positive terminals on each speaker, and negative to negative.

Step 9 – Replace the Radio and Test

You can now replace your factory radio in the dash. Make sure all connections are secure and wires are neatly routed before reinstalling. With everything hooked up properly, reconnect the battery and test out your new amp and speaker setup! Slowly increase the head unit volume while listening for clear sound.

Tips on How to Hook Up Amp to Factory Radio

Use an amp wiring kit with all necessary cables and connectors included.

• Carefully remove door panels to run speaker wires into door cavities.
• Maintain proper wire gauge when extending cables.
• Connect the remote turn-on wire at the radio harness for switched power.
• Use a hi-low converter to adapt speaker wires if needed.
• Adjust gain and crossovers for optimal amplification.
• Allow proper airflow around the amp to prevent overheating.

Benefits of Adding an Amp

Hooking up an amplifier to your factory car stereo provides plenty of benefits that enhance your driving experience:

1. More Volume – Amplifiers increase electrical current and power to your speakers, allowing much higher listening volumes. Just 20 watts per channel can make a huge difference in loudness.
2. Improved Clarity – In addition to being louder, amplified speakers will sound clearer with less distortion at high volumes. You’ll hear crisper highs and deeper lows.
3. Better Range – Amping factory speakers give them an extended frequency range to pick up bass and treble tones they couldn’t produce before. Upgraded speakers also benefit from increased headroom.
4. Signal Boost – Weak head unit outputs may not be able to drive speakers properly. Adding an amp provides a stronger signal for enhanced performance.
5. Customization – Amps allow you to tune sound with crossovers and EQ adjustments. You can create a custom listening experience tailored to your music preferences.
6. Reliability – Underpowered speakers can become damaged more easily. Amplifying them reduces strain and extends the lifespan of your system.

Choosing the Right Amplifier for Factory Stereo

When selecting an amplifier for your factory radio setup, there are a few key factors to consider:

• Power – Match the amp’s wattage to your speakers’ power handling for optimal use without blowing them.
• Number of channels – Choose a multi-channel amp to power all speakers, or individual amps per speaker.
• Input sensitivity – Match the input voltage range to the output of your radio. High-level inputs work well with factory units.
• Size and footprint – Make sure the amp dimensions fit your proposed mounting location. Heat dissipation is important as well.
• Features – Consider available crossovers, bass boost, remote gain control, and other features that enhance adjustability.
• Brand reputation – Stick with reputable, quality brands like Alpine, Rockford Fosgate, JBL, and others known for good car amps.

How to Hook Up an Amp to a Factory Stereo in Difficult Vehicles

Some vehicles present challenges when installing amps, but with creativity and diligence, it can be done in any car:

• Use spare tire wells and under-floor storage spots to conceal amps in trunks.
• Try under-seat brackets to mount smaller amps discreetly.
• Look for unused spaces around the dash to tuck away wiring.
• Run power cables under sills or along existing harness runs.
• Use audio isolation techniques to avoid noise in problematic vehicles.
• Research helpful forums and guides for tips on your specific vehicle.
• Consider custom metal fabrication for unique amp rack mounting.

While it may require extra effort, installing an amplifier in hard-to-wire vehicles is worth it for the audio rewards. Take your time routing cables neatly and the results will be superb.

Troubleshooting Common Amp Problems

Adding an amplifier should improve your car audio drastically, but issues can arise if the wiring is faulty:

• No sound – Check power/ground connections, fuses, head unit output, and RCA cables first.
• Engine whine – Ensure proper grounding and isolate or re-route RCA cables away from the vehicle harness.
• Alternator whine – Install a noise filter or isolator to condition power and deflect electrical noise.
• Overheating – Securely mount the amp for maximum airflow and use lower gain if overdriving the amp.
• Blowing fuses – Verify you have a proper fuse rating for amp wattage. Lower gain if the fuse keeps blowing.
• Lights dimming – Add capacitor or second battery wired to amp to supply needed current.
• Distorted sound – Reduce gain to match output voltage range. Also, try adjusting crossover points.
• Engine noise – Use high-quality power/ground wiring and alternator whine filters.

With good installation practices and component matching, amplifiers should provide clean, distortion-free sound. But if issues creep up, be prepared to troubleshoot.

Upgrading Speakers and Subwoofers

Adding an amplifier creates headroom to take your speakers to another level. Some options to optimize your amplified system include:

• High-end component speakers – Replace coaxial speakers with separate woofers and tweeters for better frequency response.
• Coaxial upgrade – Choose coaxials able to handle more power and with improved cone materials.
• Add a subwoofer – Install a sub for deep bass missing from factory speakers. Ideal for amp integration.
• Sound deadening – Use dampening mats on the doors to reduce vibrations for cleaner sound.
• Higher gauge wires – Run thicker power/speaker cables to maximize current flow.
• Aftermarket head unit – Consider a new receiver with pre-amp outputs and customizable sound.
• Digital signal processing – Add external EQs and crossovers for precise tuning ability.

Amping factory speakers give them a new life, but upgrading other components takes the experience even further. Building a proper sound system around your new amp provides the best listening experience.

Final Thoughts

Hooking up an amp to your factory car stereo lets you extract more power and achieve the sound you want. While it takes some legwork running wires, the audio rewards are well worth it. With proper installation and safe mounting, an amplifier can provide a seamless OEM integration that looks and sounds great. Just follow our guide on how to hook up amp to factory radio and use quality gear. Soon you’ll be enjoying louder, clearer music from your factory radio at any volume.

 

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