How do I Wire RCA Cable for Multiple Amps?

By Blaze Johnson

i Jason Grzeskowiak/Demand Media

Installing and connecting multiple car audio amplifiers into your vehicle will allow you to improve sound system quality and connect additional speakers, or make better use of high-power after-market components. Certain after-market stereo head units may feature several RCA output connections, located at the rear of the device, specifically design for external amplifiers. Connecting multiple amplifiers to an RCA audio source will provide superior signal quality over speaker level connections from the stereo head unit.


Step 1

Turn off the vehicle and open the hood.

Step 2

Disconnect the "Negative" battery cable from the battery, using an appropriate size wrench.

Step 3

Read the documentation for the head unit and determine the type and number of RCA outputs available at the rear of the device. Certain head units may include one or several RCA outputs, providing separate signals for the front and rear speaker channels, while a third subwoofer channel will handle low frequency sounds.

Step 4

Remove the bezel surrounding the head unit faceplate to expose the removal key slots, if applicable. Refer to the installation and removal instructions for the head unit for specific guidelines needed to slide the unit out from the mounting chassis.

Step 5

Insert the specially designed removal keys into the removal key slots, found near the left and right side edges of the head unit.

Step 6

Slide the head unit out of the chassis to expose the available rear RCA output connections. Disconnect the antenna cable and main wiring harness from the rear of the head unit. Place the head unit in a safe area.

Step 7

Determine the wiring path for the power cable leading to the external amplifiers. Typically, power cables run from the battery, through the vehicle's firewall, underneath the left or right side interior rocker trim molding and carpet. Never run the RCA audio cables together with the amplifier power cable; run the RCA cables underneath the opposing side of the vehicle.

Step 8

Refer to a vehicle specific repair manual for instructions related to interior trim components and bottom dash cover removal, if necessary.

Step 9

Remove the left or right side rocker trim molding and lower dash cover located inside the vehicle, using an appropriate size screwdriver. Remove the top and bottom rear seat cushions to gain better access when running the RCA cables to the rear trunk area, if applicable.

Step 10

Label each cable appropriately, according to the channel type, using masking tape and a pen.

Step 11

Run the RCA cables under the dashboard area and pull the cables through the head unit chassis opening. Leave enough slack in the cables to properly connect the RCAs to the head unit.

Step 12

Run the remaining RCA cable lengths underneath the carpet, directly below the mounting areas for the rocker trim molding. Run the RCA cables through an available wire loom opening that leads to the trunk area, if applicable. Replace the interior trim pieces.

Step 13

Connect the RCA cables to the appropriate head unit outputs. Reinstall the head unit into the mounting chassis and replace the trim bezel.

Amplifier Connections

Step 1

Connect the "Front" channel RCA cables to the "FRONT/RCA IN" jacks located on the speaker amplifier powering the front speakers. If you wish to use a four-channel amplifier for your vehicle's front and rear speakers, connect the "Rear" RCA cable to the corresponding "REAR/RCA IN" connections on the same amplifier.

Step 2

Connect the "Rear" channel RCA cables to the amplifier powering the rear speakers, when using two separate front/rear amplifiers.

Step 3

Connect the "Subwoofer" channel RCA cables to the corresponding RCA "IN" jacks for the amplifier powering the subwoofer, if applicable. If the head unit does not include a subwoofer output, you may use an available "Rear" or "Front" output as a substitute.

Step 4

Connect an extra pair of RCA cables from the subwoofer "IN" jacks to the "RCA LINE OUT" connections, located on the "Rear" amplifier, if the head unit does not feature a separate subwoofer amplifier and all other RCA output connections are in use.

Step 5

Check the amplifier connections and reinstall the rear seat cushions, if applicable. Reconnect the "Negative" batter cable to the battery and close the vehicle's hood to finish the installation process.