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General Amplifier Installation Tips

Crutchfield Writing Team — Apr 22, 2010

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General Tips
Installation photo essay

Here are a few tips to keep in mind as you plan your amp installation.

Finding the right spot

An amp can be securely installed with just a few screws. But since amps can be sensitive to electrical and motor noise and because interference from the amp may affect your radio reception, try to mount it at least 3 feet away from the receiver. Good locations include:

In the trunk or hatch area
Pros: Lots of room for large amps. Near the rear speakers or sub enclosure.

Cons: You sacrifice some cargo space. Longer wires and patch cords required.
Note: When working inside the trunk, tape over the latch, so you won't become trapped inside accidentally.
Under a seat
Pros: Closer to the receiver, so you can use shorter patch cords and signal cables. Closer to the front speakers, so running wire to them will be easier. No cargo space sacrificed.

Cons: You may have to remove the seat to do the installation (Warning: removing your seat could deactivate your vehicle's SRS system). Larger amps won't fit.

Keeping your amp cool

Something else to consider when choosing a mounting spot: Amplifiers produce heat, and the heat must be dissipated efficiently. The amp's cooling fins absorb heat and radiate it into the surrounding air. For the cooling fins to operate efficiently, they need a few inches of air space around them. When mounting the amp on a side wall, try to position it so that the slots in the cooling fins are vertical.

Amps should not be mounted on the bottom of a rear deck with the fins facing down because the heat will radiate back up into the amp. Leave yourself enough room on either side of the amp to make all the wire connections and adjust the controls. If you have a subwoofer box in your vehicle, you can mount the amp on the outside of the box.

If you are mounting the amp to the vehicle's floor, check beneath the car to be sure your screws won't puncture a brake or gas line.

Amplifier Wiring Kits

Amplifier wiring kits contain power and ground cable, a thin piece of wire for the turn-on lead, a fuse or circuit breaker, and all the connectors you need. The main power lead should be thick, since it draws power directly from the positive battery terminal. An in-line fuse or circuit breaker installed near the battery is a must. Without one, an accidental short circuit could pose a fire hazard and damage your amp.

Select the wire (10-, 8-, 4-, 2-, or 1/0-gauge) that's appropriate for your installation, depending on the length of wire you want to use, the power of your amplifiers, and how you plan to use them. For more information, check our cable gauge selection chart. Make sure that the fuse rating of your amplifier does not exceed the rating of the fuse that's included with your wiring kit — if so, you'll need to buy a larger fuse.

No preamp outputs on your receiver?

Most aftermarket receivers provide preamp output from RCA jacks. In this case, an RCA patch cable carries the signal from the receiver to the amp. If your receiver does not have preamp outputs, many amplifiers feature speaker-level inputs, which have built-in converters which step the speaker-level signal down to a preamp-level signal acceptable to the amp.

You can access the speaker-level signal by stripping a small section of your vehicle's right and left speaker wires, and splicing in wires that lead to your amp (similar to splicing into your receiver's turn on wire — see the Amplifier Installation Guide). Note: Tapping into speaker wires in this manner does not affect the performance of your speakers.

If your amp doesn't have speaker-level inputs, an effective and inexpensive line output converter will help you step the speaker-level signal down to preamp level. Then run an RCA patch cord from the converter to the amplifier. Make sure the patch cords supplying the musical signal to the amplifier are kept well away from potential sources of noise, such as brake light wires or rear window defroster wires.

Installing an amplifier calls for a little more skill and creativity than installing a receiver or a pair of speakers in the factory locations. But when the installation is done, you'll notice that the extra power will give you more volume and much cleaner, more dynamic sound, even at low listening levels. If you love music, you'll be knocked out by the difference!

Here's a step-by-step look at the entire process of a typical amp install. (Thanks to Luka Radakovic for allowing us to photograph his 1998 Ford Escort ZX2, and to Crutchfield installer Clay Sims for his patience.)

Wiring

1. Disconnect the negative terminal from your battery — this allows you to run power cable through the vehicle without risking a dangerous short circuit. Remove the red power wire from your amp wiring kit (usually 16-20 feet in length). Locate a hole on the firewall of your vehicle; most cars will have a predrilled hole you can use. If not, you'll have to find a good place to drill one — take care not to drill through a gas line or electrical wiring! For example, in a Ford with an automatic transmission (like the car pictured), there's a plate that covers the clutch pedal opening — you can drill through this plate without hitting anything. Once you've found or drilled a suitable hole, run the power wire through the hole into the engine compartment. (Install a rubber grommet in the hole to prevent damage to the power cable.)	Click to enlarge
2. Find a good spot close to your battery to place your fuse holder (included in the kit) — you'll want the section of power line between the fuse and the battery as short as possible (less than 6" is best). Cut a short piece off the end of the power wire (to cover the distance from the battery to the fuse holder location), and strip the insulation off both ends with a wire stripper. Crimp the terminal ring (included in the kit) on one end of the short piece of wire, and crimp the fuse holder to the other end. Strip the insulation off the end of the red power wire that leads into the passenger compartment, and connect it to the other end of the fuse holder. (Note: in some wiring kits, the power wire may already have an inline fuse holder installed.)	Click to enlarge
3. Connect the ring terminal to the battery, and anchor the fuseholder to a suitable spot with a self-tapping screw (smaller fuseholders may not have to be anchored). Thread the wire loom (included with some kits) over the red power cable until it reaches the firewall and cut to fit. Thread another piece over the short power wire running from the fuse holder to the battery.	Click to enlarge
4. Remove the radio from the dash to access the turn on wire (usually a blue wire). Strip the insulation off a small section of this wire coming from the radio (as pictured), wrap the blue turn on lead (included with the kit) around it, and solder it. Wrap the exposed area with electrical tape to guard against a short. You will route this blue turn on lead all the way back to your amplifier, where it connects to the amp's remote turn on terminal.	Click to enlarge
5. Connect the RCA patch cables (included with most kits) to your radio's RCA preamp outputs (tape them together so they don't come apart), and route the cable to the OPPOSITE SIDE of the vehicle from the power cable. It's important to separate the patch cables from the power wires to avoid potential noise problems. Partially reinstall the radio in the dash (not all the way, in case you have to fix a problem later).	Click to enlarge
6. Remove the door sill trim panel (it pops off on most vehicles, but check for screws before you try) on both sides of the car. Route the red power wire under the carpet down one side of the vehicle, and the RCA patch cables down the other side. The blue turn on lead doesn't carry enough current to cause interference or noise, so it doesn't matter on which side this wire goes. Replace the trim panels, and route the wiring along the rear side panels (there's usually a good place to tuck it away), around the sides of the rear seat, and into the trunk (or wherever you've decided to mount the amp).	Click to enlarge
7. Remove a bolt near the planned amp location. Scrape away any paint and clean the bolt location thoroughly (improper grounding is the #1 cause of noise problems). Crimp a ring terminal (included with kit) to the short piece of black ground cable (also in the kit), and then bolt the terminal tightly to the vehicle's metal chassis. If you can't find a convenient ground screw or bolt, drill a hole for one — be careful not to drill into the gas tank or a gas or brake line.	Click to enlarge

Amplifier 8. Mark off the amp's location on the seat back (or wherever it's going), also noting the location of the power connections, speaker outputs, and preamp inputs. Make slits in seat back fabric, and run the power, speaker, and RCA wiring under the material to the appropriate slits. A wiring snake (available at hardware and auto parts stores) is handy here — insert the snake through the slit and reach to the bottom of the seat, grab hold of the wiring with the snake's grips, and pull it through. (No wiring snake? A coat hanger will do in a pinch.)	Click to enlarge
9. Install grommets and terminals (included in wiring kit) at the ends of the power, ground, and turn on leads, and connect to the amplifier. Hook up speaker wire and RCA patch cables to the amp. Turn on the radio, and the amp should fire up. Start your car, rev your engine, and listen for any engine whine coming through the speakers. If there are no noise problems, reinstall the radio and mount the amplifier in place with dry wall screws (type of screw may vary according to the mounting location).	Click to enlarge
10. Connect speaker wires to the subwoofer box (or speakers). Adjust the gain controls on the amplifier according to the instructions in your manual. If you're hooking up a subwoofer, turn up the radio to a healthy volume level, and adjust the gain controls so the bass is well-matched to the full-range speakers. A test disc (or bass-heavy CD) is helpful for making final adjustments.	Click to enlarge
11. Put the seat back up, clean up the mess, and rock out! A Dynamat license plate kit will cure any case of rattling license plate caused by massive bass output!	Click to enlarge
For more amp installation info, see our Amplifier Installation Guide.