How to Wire a 4 Channel Car Amplifier

Written by david lipscomb Google
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How to Wire a 4 Channel Car Amplifier
Four-channel amplifiers deliver clean power in a car stereo system. (amplifier image by Darko Draskovic from Fotolia.com)

Four-channel car amplifiers offer a great degree of flexibility. Utilising a four-channel amp with direct speaker wiring to four separate channels can make a dramatic difference from the modest power supply found in car radios. Using a larger power transformer and more accurately rated power means higher dynamics with lower distortion. Additionally, four-channel amps still retain fader (adjustment of front-to-back sound intensity) capability off the radio while delivering the clarity expected from digital sources.

Skill level:
Moderately Easy

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Things you need

  • 4-channel amplifier
  • 2 pair RCA cables
  • Speaker wire
  • Small socket wrench and inserts
  • Screwdrivers (Allen, Phillips, flat head)
  • Plastic insulated t-tap connector
  • Vehicle's manual
  • Electrical tape
  • Power and ground wire
  • Fuse and fuse holder
  • Power and ground cable ring terminals
  • Drill with Phillips bit
  • Self-tapping screws
  • Klein tool

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Instructions

  1. 1

    Make sure the vehicle is turned off. Open the bonnet, and using the small socket wrench and appropriate-size insert, unscrew the negative battery terminal. Secure this terminal with electrical tape.

  2. 2

    Determine the distance from the battery to the amplifier's mounting location. Cut this length of power wire using the Klein tool. Strip off 1/4 inch of insulation from this wire on one end. Use the crimper on the Klein tool to connect the ring terminal to the end connecting to the battery.

  3. 3

    Cut off no more than 18 inches off the end of the power cable (ring terminal on one end, cut wire on the other). Strip off 1/4 inch of insulation from both ends of the wire. Insert the bare wires into the opposing ends of the fuse holder, consulting the holder's manual for internal fuse connection options. Many people connect via set screw, while others wrap the wire around the connection post and screw the post in the holder.

  4. 4

    Unsnap the plastic trim running down the side of the car, which holds the carpet down. Use 4-inch plastic zip ties to safely connect this wire next to factory-installed cables. Route the power wire through the access grommet (look for a rubber bushing with wires disappearing into the cabin from the engine compartment) on the vehicle's firewall to the channel under the trim. Be sure to remember to keep the wire away from snags from pedals and feet.

  5. 5

    Cut a length of ground wire, not longer than 12 inches. Use the Klein tool to strip off 1/4 of insulation from each end of the wire. Crimp on a ring terminal to one end of the ground wire.

  6. 6

    Find a suitable location for amplifier. Remember to carefully inspect the spot for damage to fuel and brake lines from screws, and make sure to keep the unit away from foot traffic. The amplifier should have at least 3 inches of ventilation. This location may be under a seat or in the boot. Use the drill and self-tapping screws to mount the amplifier to this location.

  7. 7

    Consult the vehicle's manual to determine the proper way to gain access to the rear of the radio. Place the screws in a safe place for radio reinstallation.

  8. 8

    Route two pairs of RCA cables from the radio to the amplifier on the opposite side of the power wire. Make sure to avoid potential traffic areas and crush hazards from passengers. Connect the RCAs from the front radio pre-outs to RCA input channels 1 and 2 and the rear RCAs to inputs 3 and 4.

  9. 9

    Determine the length of remote turn-on wire required to run from the rear of the radio to the amplifier. While the rear of the radio is exposed, use a plastic t-tap to connect the 16-gauge remote lead from the blue "REM" wire on the radio's harness. Route this cable next to the power wire running from the battery.

  10. 10

    Take note of the speaker wire's polarity. Positive wire is indicated by a ridge or other marking. Strip off 1/4-inch of insulation from each speaker wire using the Klein tool, and twist the bare wire tightly to ensure no frays are present. Screw in the positive terminal of the wire to speaker output channel 1; do likewise for the corresponding negative wire on the same channel. Repeat this process for all four speakers. When routing wire to the speaker make sure that the polarity of the amplifier matches the connection on the speaker.

  11. 11

    Use the Klein tool to strip off 1/4 of insulation from the power lead. Be sure to make the cut away from the amp to prevent wire frays from accidentally entering the chassis of the unit. Connect power, remote and ground to the amplifier, using the appropriate screwdriver. Make sure no frayed wires are protruding from under the terminals to prevent a short.

  12. 12

    Connect the end of the ground wire with the ring terminal, and attach it to a section of bare metal on the vehicle using the drill and self-tapping screw. Remove paint with the end of a flat head screwdriver.

  13. 13

    Return to the engine compartment. Insert a fuse whose value matches the internal fuse ratings on the amplifier. Slide the power lead's ring terminal over the positive battery post, securing the connection with the socket wrench and appropriate insert. Do the same with the vehicle's negative battery terminal.

  14. 14

    Return the radio to its installed location. Turn on the vehicle, and turn down the volume on the radio in case a short is present.

Tips and warnings

  • An easy way to set amplifier gain is to turn them all the way down, then turning the radio to 3/4 maximum volume. Slowly turn up the gain of each channel until distortion is present, then turn the gain down gradually until it disappears.
  • If fuses keep blowing, inspect the installation for loose power or ground connections. Also, be sure to inspect for pinched or cut wires.
  • Never run a power cable through a door jamb for access to the cabin. This wire will become pinched over time, and cause a dangerous short.

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