How To Hook Up Amp To Factory Stereo

So, you're looking to crank up the volume in your ride without ditching your factory stereo? Maybe you appreciate the integrated look of your original head unit, or perhaps you're avoiding the cost and complexity of a full aftermarket replacement. Whatever your reason, adding an aftermarket amplifier to a factory system is a common and achievable upgrade. However, it's not always a plug-and-play affair. This guide dives deep into the methods, considerations, and potential pitfalls of hooking up an amp to your factory stereo.

The Problem: Insufficient Power

Factory car stereos are designed with a focus on efficiency and affordability. The built-in amplifiers within these units typically deliver a modest amount of power, often around 15-25 watts RMS per channel. This is sufficient for everyday listening, but it often falls short when you crave louder volumes, deeper bass, or a more dynamic soundstage. Think of it like trying to power a concert hall with a desk lamp – it simply can't deliver the necessary intensity.

The solution: An external amplifier steps in to provide the necessary power boost. By taking the low-level audio signal from the factory stereo and amplifying it, you can drive aftermarket speakers with the headroom they need to perform optimally. This results in cleaner, louder sound with less distortion.

Understanding the Signal Chain

To successfully integrate an amplifier, it's crucial to understand how audio signals flow through your car's system. The factory head unit acts as the source, generating a low-level audio signal. This signal is then processed (e.g., for volume, tone control) and sent to the built-in amplifier. From there, amplified signals are sent to the speakers.

High-Level vs. Low-Level Inputs

This is where things get interesting. Aftermarket amplifiers typically accept two types of input signals:

Low-Level (RCA) Inputs: These are the preferred method, offering the cleanest signal transfer. They expect a line-level voltage signal, typically around 0.5 to 2 volts. Think of it as the difference between a whisper and a normal speaking voice.
High-Level (Speaker-Level) Inputs: These inputs accept the amplified signal that would normally go to the speakers. The amplifier internally attenuates this higher-voltage signal down to a level it can handle. Consider this the amplified "voice" after the factory stereo's internal amplifier has already done its job.

The challenge: Factory stereos often lack RCA outputs. This is where Line Output Converters (LOCs) become essential. An LOC takes the high-level speaker output from your factory stereo and converts it into a low-level RCA signal that your aftermarket amplifier can use.

How an LOC Works: The Resistor Network

At its core, an LOC is a simple device containing a resistor network. These resistors reduce the voltage of the speaker-level signal to a level suitable for RCA inputs. Think of it as a volume knob that only goes down. The quality of the resistors and the overall design of the LOC directly impact the audio quality. Cheaper LOCs can introduce noise and distortion, negating some of the benefits of adding an amplifier.

Analogy: Imagine filling a swimming pool with a fire hose. The hose delivers too much water pressure, potentially damaging the pool. An LOC acts like a valve, reducing the pressure to a manageable level for a garden hose – the pressure will fill the pool just as well, but without the risk of damage.

Connecting the Amplifier: Step-by-Step

Here's a generalized guide to connecting your amplifier, acknowledging that specific steps may vary depending on your vehicle and equipment:

Identify Speaker Wires: You'll need to tap into the speaker wires coming from your factory head unit. Use a wiring diagram specific to your car model to identify the correct wires. A multimeter can also be used to verify polarity.
Install the LOC: Connect the LOC to the identified speaker wires. Ensure proper polarity (positive to positive, negative to negative). Many LOCs require a ground connection.
Run RCA Cables: Connect RCA cables from the LOC's output to the amplifier's input.
Power Wiring: This is arguably the most crucial step. Run a heavy-gauge power wire directly from the car battery to the amplifier. Always use a fuse within 18 inches of the battery to protect the electrical system.
Grounding: Connect the amplifier's ground wire to a clean, solid metal point on the car's chassis. Ensure the contact point is free of paint and rust. A poor ground can introduce noise and degrade performance.
Remote Turn-On: The amplifier needs a signal to turn on and off with the car. This is typically a 12V signal. In factory systems, finding a reliable remote turn-on wire can be tricky. Some LOCs have a built-in remote turn-on output that activates when they detect a speaker signal. Alternatively, you can tap into an accessory power wire that turns on with the ignition.
Connect Speakers: Connect the amplifier's speaker outputs to your aftermarket speakers, ensuring proper impedance matching.
Tuning: Once everything is connected, carefully adjust the amplifier's gain settings to match the output of the LOC and the sensitivity of your speakers. This is critical to avoid distortion and damage.

Pros and Cons of Adding an Amplifier to a Factory Stereo

Pros:

Improved Sound Quality: Cleaner, louder sound with more headroom.
Retain Factory Aesthetics: Keep the integrated look of your original head unit.
Cost-Effective: Often cheaper than a complete aftermarket system replacement.
Expandability: Add subwoofers or additional speakers without replacing the head unit.

Cons:

Complexity: More involved installation compared to simply replacing speakers.
Potential Noise: Poorly installed LOCs or grounding issues can introduce noise.
Limited Customization: Factory head units often lack advanced EQ or crossover settings.
Integration Challenges: Some factory systems are tightly integrated with other vehicle functions, making modification difficult.

Use Cases and Manufacturer Examples

Adding an amplifier to a factory stereo is particularly useful in these scenarios:

Adding a Subwoofer: Many users want to improve bass response without changing the factory head unit. An LOC and a mono amplifier are ideal for this.
Upgrading Door Speakers: Replacing weak factory speakers with higher-quality aftermarket speakers can significantly improve sound quality. An amplifier provides the necessary power to drive these speakers effectively.
Overcoming Low Volume: Some factory systems are simply underpowered, even at maximum volume. An amplifier can provide the extra boost needed for a more enjoyable listening experience.

Manufacturer Examples: Several companies specialize in LOCs and integration solutions. AudioControl is a well-regarded manufacturer known for its high-quality LOCs with features like AccuBASS, which restores lost bass frequencies. PAC Audio offers a wide range of integration interfaces designed to simplify the process of adding aftermarket components to factory systems. JL Audio provides amplifiers with advanced features like differential-balanced inputs, which help eliminate noise and interference.

Real-World Considerations and Recommendations

While adding an amplifier to a factory stereo can be a rewarding upgrade, it's essential to approach the project with careful planning and execution. Here are some practical tips based on real-world experiences:

Research Your Vehicle: Before you start, thoroughly research your car's audio system. Wiring diagrams are essential. Websites like Crutchfield often provide vehicle-specific information.
Invest in Quality Components: Don't skimp on the LOC, wiring, or amplifier. Using high-quality components will minimize the risk of noise and ensure long-term reliability.
Proper Grounding is Key: A solid ground connection is crucial for optimal performance and to prevent noise. Use a star grounding technique if possible, connecting all ground wires to a single point.
Start Small: If you're new to car audio, consider starting with a simple subwoofer upgrade before tackling a full system overhaul.
Seek Professional Help: If you're unsure about any aspect of the installation, don't hesitate to seek professional help. A qualified installer can ensure that the system is installed correctly and safely.
Beware of Bass Roll-off: Many factory systems employ bass roll-off at higher volumes to protect the factory speakers. An LOC with bass restoration features (like AudioControl's AccuBASS) can help compensate for this.

Ultimately, adding an amplifier to your factory stereo can be a great way to enhance your listening experience. By understanding the fundamentals, carefully selecting your components, and following proper installation techniques, you can achieve a significant improvement in sound quality without sacrificing the integrated look of your factory system.