Audio Wiring / September 5, 2018 / Bristol London.
Connect the Power and RCAs, then reconnect the negative battery terminal. Re-install the head unit and play some music, making sure everything is connected correctly.
Connect the radio to a constant 12-volt source, an ignition lead, the amplifier turn-on, and the antenna. On newer cars, the constant 12-volt and the ignition wire connections can be made through the factory wire harness. On older cars, the fuse block can serve as the continuous 12-volt source.
Sometimes a power amplifier comes equipped with unique features. The car audio crossover can add to a car amplifier. A car crossover allows the amplifier to divide the music by frequency. The split signal becomes strengthened by the amplifier and then leaves the amp and proceeds to another part of the car speaker system.
You’ll need to run the wire into the passenger compartment. For this, you need an unused grommet, which is just a fancy word for a plug. You might find a large grommet and poke another hole in it. As a last resort, you might have to drill the firewall of your car and install an aftermarket grommet.