How to Connect Multiple Ground Wires for a Car Stereo

By David Lipscomb

Multiple grounds are needed with multiple amplifiers.
i Matthew Peyton/Getty Images Entertainment/Getty Images

In any car stereo system, regardless of total power, the ground wiring is every bit as important as power and signal wiring. Ground wires complete the circuit from the battery, so without proper grounding, nothing works. Using proper techniques, such as bolting the ground to bare metal, helps ensure system noise is minimized and reliability increased. This is especially true when grounding multiple amplifiers and devices, with ground loops and intermittent operation threatening quality sound.

Grounding Primer

Regardless of where the amplifiers are mounted, the common ground should always be as close as possible to the devices. Placed no more than 18 inches from the mounting location, grounding locations are always bare metal, using a crimp-on ground ring and star washer to increase contact while resisting vibration. At no time should seatbelt bolts or welded chassis locations be chosen for grounding locations, as these do not provide quality continuity. Regardless of the number of devices you're grounding in any system, these rules are basics that must be followed.

Multiple Grounds

Ground blocks make grounding multiple in-car electronic items easy. Featuring multiple threaded connectors and solid mass, these units receive each ground wire from amplifiers, equalizers, processors and even the head unit. Total amperage of all stereo system devices connected to the vehicle battery dictates the size of power wire selected to run to the positive distribution block. Ground wires are equal in gauge to power wires to maintain proper continuity. A common scenario involves a positive ground block connected to the battery via 0-gauge wire, with each amplifier connected to that same block using 8- or 4-gauge wire. The corresponding and separate ground block receives ground wires of the same gauge, with a 0-gauge ground wire connected to the chassis.

Safety and Reliability

Removing the ground wire when a car audio system is turned on will create sparks and possibly fire and equipment damage. Loose connections or ground wires simply taped to the chassis results in amplifiers turning on and off, going into protection mode and potential damage. Periodically check the integrity of the ground wire connection to the chassis, ensuring it's tight and lacking corrosion. You can help this by applying a thin coating of silicone caulk over the finished ground connection, sealing out moisture.

Random Grounding Locations

Home audio manufacturers often market using common internal grounding locations as an indicator of a high level of build quality. There's good reason for this. Ideally each ground should measure at zero volts DC. However, this is rarely the case and fluctuates depending on chassis location. Despite this, star or common grounding prevents different devices from "seeing" different ground potentials, preventing ground loops in most scenarios. Quiet, quality grounds create silent backdrops for music, increasing perceived dynamic range and generally reducing annoying whine and hiss. Tough ground loop problems can be mitigated using an in-line ground loop isolator, but this masks the problem as opposed to solving it.