The power wiring circuit carries current from the vehicle’s battery to the amplifier or amplifiers in the system. It is the most current-intensive wiring run in a car audio installation, and getting it right is critical for both performance and safety.
The circuit consists of three main elements: the positive cable running from the battery’s positive terminal to the amplifier’s power input, a fuse holder positioned close to the battery, and the negative cable connecting the amplifier’s ground terminal to the vehicle’s chassis. The positive run is typically the longest cable in the system, often passing through the firewall and running beneath trim panels to reach an amplifier mounted in the trunk or under a seat.
Wire gauge selection is based on total system current draw, which is determined by dividing total system power by the supply voltage and accounting for efficiency losses in the amplifier. A rough rule of thumb is that 1,000 watts of amplifier power at 14.4 V requires approximately 80–90 amperes of current, which calls for at least 4 AWG wiring for typical run lengths. Higher-power systems require proportionally heavier gauges — 1/0 AWG or larger is not uncommon in high-output builds.
The fuse protecting the positive cable must be rated to protect the wire, not the amplifier. It should be located as close to the battery terminal as practical — within 18 inches is a common guideline. In the event of a short circuit anywhere along the positive run, this fuse is the only protection between the fault and a potential fire.
Grommets are used wherever the power cable passes through metal panels or the firewall to prevent the cable’s insulation from chafing against bare metal edges, which over time can create a short circuit.
Taking care with power wiring from the start eliminates the most common causes of amplifier failure and electrical fires in aftermarket audio installations.