How To Bypass The Factory Amp

So, you're looking to bypass the factory amplifier in your car audio system? Maybe it's failing, or perhaps you're aiming for a significant audio upgrade that the stock amplifier simply can't handle. Whatever the reason, bypassing it is a common task for serious car audio enthusiasts. It's not always straightforward, and understanding the process is crucial for a successful and safe modification. This guide will walk you through the technical considerations, pros, cons, and step-by-step methods for bypassing your factory amp.

The Problem: Why Bypass the Factory Amp?

Factory amplifiers, while adequate for most casual listeners, often become a bottleneck when upgrading other components like the head unit or speakers. Imagine it like this: you've upgraded your home theater's Blu-ray player to the latest 4K model and bought a stunning new OLED TV, but you're still using the same old, entry-level receiver from 10 years ago. The receiver, the weak link, prevents you from truly experiencing the enhanced picture quality. The factory amp is often the same situation in a car audio system.

Here's a breakdown of the common reasons to bypass:

• Power Limitations: Factory amplifiers typically have limited power output. If you're installing aftermarket speakers that require more power, the factory amp won't be able to drive them effectively, resulting in distortion and poor sound quality.
• Signal Processing: Many factory amps incorporate built-in equalization curves or other signal processing designed to compensate for the limitations of the stock speakers and cabin acoustics. These settings can conflict with aftermarket components and negatively impact sound quality.
• Lack of Features: Factory amps often lack features found in aftermarket amplifiers, such as adjustable gain, crossover settings, and bass boost.
• Reliability Issues: Older factory amps can simply fail due to age, heat, or component degradation. Bypassing a failing amp is often more cost-effective than replacing it with another factory unit.
• Integration Problems: Some aftermarket head units are designed to directly drive speakers without an amplifier. In such cases, the factory amp becomes redundant and can even interfere with the signal path.

Understanding How the System Works: A Deep Dive

To effectively bypass the factory amp, you need to understand its role in the car's audio system. Here's a simplified overview:

1. Head Unit: The source of the audio signal (radio, CD player, etc.).
2. Factory Amplifier: Amplifies the low-level signal from the head unit.
3. Speakers: Convert the amplified electrical signal into sound.

The factory amplifier usually sits between the head unit and the speakers. It receives a low-level signal (often referred to as a line-level signal) from the head unit and boosts it to a higher voltage level that can drive the speakers. The crucial part here is understanding that the factory wiring is designed specifically for this arrangement.

Mechanically, bypassing the amp means rerouting the audio signal directly from the head unit to the speakers, effectively removing the amplifier from the equation. However, you can't just unplug the amp and expect things to work. Here's why:

• Wire Gauge: Factory speaker wiring is often thin, designed for the low power output of the factory amplifier. If you're installing a high-power aftermarket amplifier, you'll likely need to upgrade the speaker wiring with thicker gauge wire to handle the increased current.
• Impedance Matching: Speakers have a characteristic impedance (measured in ohms). The amplifier needs to be properly matched to the speaker impedance to deliver power efficiently and avoid damage. Factory amplifiers are designed to work with the specific impedance of the factory speakers. If you change speakers, you need to ensure the amplifier (factory or aftermarket) is compatible.
• Wiring Harnesses: Factory amplifiers typically use proprietary wiring harnesses that are not directly compatible with aftermarket components. You'll need to either adapt the existing harnesses or run new wiring.
• Remote Turn-On: Aftermarket amplifiers require a remote turn-on signal from the head unit to switch on and off. The factory amplifier may or may not have a dedicated remote turn-on wire.

Methods for Bypassing the Factory Amp

There are several ways to bypass a factory amp, each with its own advantages and disadvantages:

1. Direct Wiring (The "Hard Way")

This involves cutting the wires connected to the factory amp and splicing them directly to the corresponding wires from the head unit. This is the most labor-intensive method but offers the most control. It's generally not recommended unless you have extensive experience with car audio wiring.

2. Wiring Harness Adapters (The Recommended Way)

Wiring harness adapters are plug-and-play connectors that allow you to interface with the factory wiring without cutting any wires. They connect to the factory amp's input and output harnesses, allowing you to reroute the signal as needed. This is the safest and easiest method for bypassing the factory amp. Companies like Metra and Scosche specialize in creating these adapters.

Here's the general process using wiring harness adapters:

1. Identify the Factory Amp: Locate the factory amplifier in your vehicle. It's often located under a seat, in the trunk, or behind the dashboard.
2. Purchase the Correct Wiring Harness Adapters: Find adapters that are specifically designed for your vehicle's make, model, and year. Crutchfield and other online retailers can help you identify the correct adapters.
3. Connect the Adapters: Plug the input adapter into the factory amp's input harness (the wires coming from the head unit).
4. Connect the Output Adapter: Plug the output adapter into the factory amp's output harness (the wires going to the speakers).
5. Reroute the Signal: The adapters will typically have wires that allow you to connect the head unit's speaker outputs to the speaker wires on the output adapter, bypassing the factory amp. This may involve some simple wire splicing or crimping.
6. Connect Remote Turn-On: If you are installing an aftermarket amplifier, connect the remote turn-on wire from the head unit to the remote turn-on wire on the adapter.

3. Using a Line Output Converter (LOC)

A Line Output Converter (LOC) is a device that converts the high-level speaker outputs from the factory head unit into low-level RCA outputs that can be connected to an aftermarket amplifier. This method is useful if you want to retain the factory head unit but add an aftermarket amplifier to power your speakers. It essentially *taps* into the signal before it reaches the factory amp, and sends it to the new amplifier.

Here's the general process using a LOC:

1. Tap into Speaker Wires: Connect the LOC to the speaker wires coming from the factory head unit. You can usually find these wires behind the head unit or at the factory amplifier.
2. Connect RCA Cables: Connect RCA cables from the LOC's output to the input of your aftermarket amplifier.
3. Connect Remote Turn-On: Connect the remote turn-on wire from the head unit (or a suitable switched 12V source) to the remote turn-on wire on the aftermarket amplifier.
4. Ground the Amplifier: Ensure the aftermarket amplifier is properly grounded to the vehicle's chassis.

Pros and Cons of Each Method

Direct Wiring

• Pros: Most direct control, potentially lower cost (no adapters needed).
• Cons: Most labor-intensive, highest risk of wiring errors, can damage factory wiring if done incorrectly, difficult to reverse.

Wiring Harness Adapters

• Pros: Safest and easiest method, preserves factory wiring, relatively easy to reverse.
• Cons: Can be more expensive than direct wiring, requires finding the correct adapters for your vehicle.

Line Output Converter

• Pros: Allows you to retain the factory head unit, relatively easy to install.
• Cons: Can introduce noise and distortion if the LOC is of poor quality, requires additional wiring.

Use Cases and Manufacturer Examples

Use Case 1: Upgrading Speakers with an Aftermarket Amplifier

Scenario: You want to replace your factory speakers with higher-quality aftermarket speakers and power them with a new amplifier.

Method: Use wiring harness adapters to bypass the factory amp and connect the new amplifier to the speaker wires. This will provide the new speakers with the power they need and bypass any signal processing from the factory amplifier.

Use Case 2: Retaining the Factory Head Unit While Adding a Subwoofer

Scenario: You want to add a subwoofer to your car's audio system but don't want to replace the factory head unit.

Method: Use a Line Output Converter (LOC) to tap into the rear speaker wires and connect them to a subwoofer amplifier. This will allow you to add a subwoofer without modifying the factory head unit.

Manufacturer Examples:

• Metra: A leading manufacturer of wiring harness adapters for car audio installations.
• Scosche: Another popular manufacturer of wiring harness adapters and other car audio accessories.
• AudioControl: A well-known manufacturer of Line Output Converters (LOCs) and other signal processing devices.

Real-World Insights and Recommendations

Before you begin, carefully research your vehicle's audio system. Consult online forums, car audio experts, and wiring diagrams to ensure you have a clear understanding of the factory wiring and the location of the amplifier.

Here are some additional tips:

• Disconnect the Battery: Always disconnect the negative terminal of the car battery before working on the electrical system to prevent short circuits and potential damage.
• Use Quality Tools: Invest in a good set of wire strippers, crimpers, and a multimeter.
• Solder Connections: For the most reliable connections, solder the wires together and use heat shrink tubing to insulate them. Crimp connectors can work, but soldering provides a stronger and more durable connection.
• Label Wires: Label all wires clearly before disconnecting them to avoid confusion during reassembly.
• Test Before Reassembling: After making the connections, test the system before reassembling the dashboard or interior panels. This will allow you to identify and correct any problems before putting everything back together.

Bypassing a factory amplifier can be a rewarding experience that significantly improves your car's audio system. By understanding the technical aspects of the process and following these guidelines, you can successfully bypass the factory amp and enjoy a superior listening experience.