How to Install a Car Amplifier | 12 Volt Outlet

A good amp install is quiet, safe and makes every watt you paid for. A bad one blows fuses, whines with the engine and can start a fire. Here is how we install amps in the bay, step by step.

SkillBeginner friendly

Time3 to 5 hours

Key partAmp install kit

Free toolPower Planner

What you need
1. Plan it
2. Wire size
3. Power and fuse
4. Ground
5. RCA and remote
6. Mount
7. Speakers
8. Set gains
Mistakes

What You Need Before You Start

Your amp and its manualRMS power, fuse size and wiring layout.
Amp install kitPower, ground, remote, fuse holder and terminals. Grab an amp install kit or a full wiring kit.
RCA cablesLong enough to reach the trunk. Shop RCA cables.
Speaker wireFrom the amp to your subs or speakers. Shop bulk speaker wire.
Factory radio?You need a line output converter to get a signal.
Basic toolsStrippers, crimpers, drill, sockets, zip ties and a multimeter.

Step 1 Plan the Install

Before you pull a single panel, decide where the amp goes and how each wire gets there. Power runs down one side of the car. RCA and remote run down the other side. Keeping them apart is the easiest way to stop alternator whine.

From the bayPick an amp spot with airflow that will not get kicked, soaked or covered by luggage. A board behind the seat or on the trunk wall works great.

Car amplifier wiring diagram showing fused power wire, short ground, RCA and remote wire routing — The four wires every amp needs, and which side of the car each one runs on.

Step 2 Pick the Right Wire Size

Wire size comes from how much current your amp pulls, not from the number printed on the box. Take the RMS power, divide by about 11 (that is 80% efficiency at 13.8 volts) and you have your current draw. Our example 1,000 W amp pulls about 90.6 amps, so it gets 1/0 OFC.

Skip the mathOur free Power Planner does the current math and tells you when you need the Big 3 or a second battery.

Car amplifier power wire gauge chart from 8 AWG to 1/0 AWG by amp wattage and current draw — Wire size by amp power. Use OFC copper and go bigger if you are unsure.

Step 3 Disconnect the Battery and Run Power

Disconnect the negative battery terminal first. Find a factory grommet in the firewall, or drill a new hole and protect it with a grommet so the wire never rubs bare metal. Run the power wire to the trunk under the trim, away from pedals and seat rails.

Fuse it firstMount the fuse holder within 18 inches of the battery. The fuse protects the wire, so match it to your wire size and amp, never bigger. Shop fuse holders and fusing and distribution.

Step 4 Ground It Right

Most amp problems we fix are ground problems. Keep the ground under 18 inches, use the same size wire as your power and bolt it to bare metal. Sand off the paint, use a ring terminal and a star washer, then snug it down tight.

Quick checkSet your meter to ohms and test from the ground point to the battery negative. You want almost zero.

Good amplifier ground on bare sanded metal compared with a bad ground on painted metal — A short, tight ground on bare metal. Paint and seat bolts cause heat, whine and shutdowns.

Step 5 Run the RCA and Remote Wire

Run your RCAs and the remote turn-on wire down the opposite side of the car from the power wire. The remote wire connects to the blue or blue and white amp turn-on lead behind an aftermarket radio. With a factory radio, a line output converter gives you a signal, and many can turn the amp on for you.

Step 6 Mount the Amp

Screw the amp to a solid board, not straight to the car body or the sub box. Leave a couple of inches around it for air. Never mount it where it can get wet, and keep it off the trunk floor if you haul a lot of gear.

Step 7 Connect Your Speakers or Subs

Wire your subs or speakers to the amp at an impedance it is rated for. Check every connection twice and make sure no stray strands touch. Not sure how to wire your subs? Our Woofer Wizard shows every option, and Amp Matchmaker helps you pick an amp that fits.

Then power upReconnect the battery, turn on the radio and check that the amp powers on with no protect light.

Step 8 Set Your Gains the Right Way

The gain is not a volume knob. It matches the amp to your radio's signal. Set it too high and you send clipped, distorted power that kills speakers. A cheap multimeter makes it easy. Our 1,000 W amp at 1 ohm has a target of 31.6 volts.

From the baySet the gain with the speakers unplugged, then reconnect them and listen. If it distorts before full volume, back the gain down a little.

How to set car amplifier gain with a multimeter using target voltage from watts and ohms — Target voltage equals the square root of watts times ohms.

Common Mistakes We See

No fuse, or a fuse far from the battery
Grounding to paint or a seat bolt
Power and RCA run together
Wire too small for the amp
Gain used as a volume knob
Bass boost cranked all the way

Power Planner car audio battery and big wire calculator with results for a 1,000 watt amplifier

Free 12 Volt tool

Let Power Planner Size It

Enter your alternator and your amp power. Power Planner shows your current draw, how much battery you need and how many big wire runs to bring to the back.

Plan My Power