You can think of an amplifier as the heart of a car audio system. And just like your ticker, you have to take good care of your amp to keep it pumping out juice. When something goes wrong with your heart, it affects not only your circulatory system, but your entire body. Likewise, if something goes wrong with your amplifier, it can have dire consequences.
Gathering the Facts
Amplifiers are the most daunting car audio components to install correctly. First, you have to decide where to mount your amps. Some components have really obvious locations. Although many stock premium car audio systems come with separate amplifiers, they are usually small, nondescript silver boxes designed to fit inconspicuously in a vehicle.
Amplifiers are the most complex car audio components to successfully and safely integrate into a vehicle. While most speaker installations are pretty straightforward and many head units can be installed by do-it-yourselfers, amplifiers present a unique set of install challenges, and the job may be best left to a professional.
Getting Comfortable With Your Charging System
To your car's battery, a car audio amplifier is just another current-consuming device. Auto manufacturers design a vehicle's electrical system to handle the total load that all of the car's electrical device can place on it, and then some.
But at what point does your car's electrical system say enough is enough? That depends on how much you demand of it. Fortunately, music is transient in nature, meaning there are lulls that don't require a lot of extra power and there are crescendos, as well as peaks - or in the car audio sense, ground-pounding bass notes - that do. It's during these transient peaks that a car's electrical system can be taxed to the max.
The amount of current drawn from the electrical system depends on the amplifier.
Deciding Where to Plant Your Power
Although speakers have their own critical placement issues having to do with sound, amplifiers have different location concerns. A good salesperson or installer at a car audio specialty store will know whether a certain amp can work well in the location you're thinking about installing it. Most amps will perform just fine when mounted under the front seats of a vehicle and will get enough airflow to keep cool.
Many people also choose to mount their amplifiers on the back of a big subwoofer box. Although, the constant vibration from the deep bass can potentially harm the internal components of an amplifier.
Rack it up
Some high-end car audio systems sport an amp rack on which multiple amplifiers can be mounted. Racks can be as simple as a piece of wood covered in carpet or as elaborate as a metal or fiberglass sculpture-like creation complete with lights, motorization, mirrors, and, in some extreme cases, even waterfalls.
An amplifier is the one component in a car audio system that directly ties to all of the others. It taps power from the car's battery, gets an audio signal from the head unit, and sends an amplified signal to the speakers.
So, the constraints of wiring also play a role in where you mount your amplifier. With all of the wires running to and from an amp, you'll want it in a location that's relatively accessible for making those connections.
Most people tend to mount amplifiers in the trunk - on the floor, on one of the side walls, or the front wall. In hatchbacks and SUVs, they likewise go in the cargo area, and in trucks behind the seats. But you can't just stick amps anywhere because they need a solid surface to mount on.
Allowing for Inputs and Outputs
Every amplifier has inputs and output, sometimes on opposite ends and sometimes arrayed together.
The inputs will include RCA jacks that accept a low-level or un-amplified audio signal, although some amplifiers will also have inputs for high-level or amplified outputs from a stock head unit. There's also usually a connection for a remote turn-on lead from the head unit to tell the amp to wake up when the system is turned on. Besides telling the amplifier that it's time to wake up and pump juice to the speakers, this turn-on scheme also ensures that your amplifier is not sucking power from your battery when the head unit isn't on.
Structuring Wire Runs
One of the most daunting tasks of installing a car audio system is running all of the wiring to and from the amp. Snaking power wires until they all end up at the amplifier is a task that calls for skill, resourcefulness, and a cool head.
On top of this routing obstacle course, you have to make sure that all of the wiring is routed in a way that ensures it won't get damaged or pinched.
Before you take on wiring up an amplifier for the first time, you should know what you're getting into.
Making a Fuss Over Fuses
An amplifier gets its power from a car's battery, which is part of your car's electrical system. If you decide to install the amp yourself, it's of paramount importance that you understand the principles of proper fusing.
Getting in Line
But even more important than an external fuse is the in-line fuse on the power wire that runs from the car's battery to the amplifier. Although the in-line fuse also protects the amplifier from a short in case something happens to the wire, more importantly, it safeguards the automobile and its electrical system. Think of the in-line fuse as a fire break: In the case of an accident, when a short circuit creates an electrical fire, the fuse opens the circuit to prevent current from continuing to flow.
Most professional installers place the amplifier power cord's in-line fuse as close to the car's battery as possible. That way, if there's a short, the fire doesn't travel far. Just imagine how far the fire would travel before it's automatically put out if, say, you decided to mount the in-line fuse in the trunk!
Respecting the Fuse Ratings
One of the cardinal rules of car audio is that you must always use the proper fuse for a given wire size. That means never substituting a fuse or replacing a blown fuse with one of a higher rating. Inversely, never replace a wire supplied or recommended by a car audio equipment manufacturer with a smaller gauge wire. Otherwise, you risk damaging your components and your car. The rating of an in-line fuse should be as large or slightly larger than the one for the amplifier.
Besides a power wire, your amplifier also needs a ground wire. The ground wire needs to be the same size as the power cable and has to be attached to a solid metal part of the car. It also should be as short as possible so that it doesn't add electrical resistance. A short ground wire also reduces the chance that the wire will pick up electrical interference and therefore introduce noise into the system.
But if there's no easy grounding point nearby, you can create your own by drilling a small hole into a metal part of the car - just make sure you know what's on the other side before you start drilling - and then inserting a sheet metal screw along with a star washer that the ground wire can in turn be attached to.
Separation of Power
One of the most common sources of unwanted noise in a car audio system comes from RCA cables carrying low-level audio signals coming into close proximity to parts of the vehicle that radiate Electromagnetic Interference. Some of the biggest culprits are components that require a lot of juice: motors for power seats, power windows, and convertible tops.
That's why it's important to route signal cables as far as possible from potential noisemakers. Of course, car audio power wires also radiate EMI, so it has become standard operating procedure for installers to route signal cable on one side of a vehicle and power wiring along the other, so that they are as far apart from one another as possible.
From Car Audio for Dummies, copyright © 2008 by John Wiley & Sons, Inc., Hoboken, New Jersey. Used by arrangement with John Wiley & Sons, Inc.