Remote Turn-on Wire
The remote turn on wire goes to the head unit. When the radio is on, it puts out 12 volts that turn the amplifier on. If you are using a factory radio that does not have a remote turn on (or power antenna wire) you can tap into, hook it up to the ignition, so that the amplifier does not remain on when you turn the car off.
If you are using multiple devices (amplifiers, crossovers, equalizers, fans, etc), you might have to add a relay, since typical turn-on wires in a radio can’t handle more that 300mA.
Even though amplifiers are easy to install, a lot of things could go wrong. The most important thing to consider is where to get the power from: Straight from the battery. ALWAYS put a fuse as close to the positive battery terminal as possible. If the wire going to the back of the car shorts out, then the fuse will blow. If you don’t install a fuse or breaker and the wire shorts out, then the wire will carry so much current that the insulation will melt and could catch your car on fire. The size of the fuse should be the same rating as the fuses used by the amp(s) or less. The ground (-) should be hooked-up to a metal part of the car. It is not necessary to run a ground wire all the way to the battery.
It is not essential to spend a lot of money in getting 99.999999% copper 0-gage wire and gold connectors unless you are installing a competition system. Here’s a table to help decide what gauge wire to use, based on total current draw and length of wire:
|Power Cable Calculator|
Draw of System
|Up to 4 ft.||4 to 7 ft.||7 to 10 ft.||10 to 13 ft.||13 to 16 ft.||16 to 22 ft.||22 to 28 ft.|
|0 – 20||14||12||12||10||10||8||8|
|20 – 35||12||10||8||8||6||6||4|
|35 – 50||10||8||8||6||4||4||4|
|50 – 65||8||8||6||4||4||4||2|
|65 – 85||6||6||4||4||2||2||0|
|85 – 105||6||6||4||2||2||2||0|
|105 – 125||4||4||4||2||0||0||0|
|125 – 150||2||2||2||0||0||0||00|
The above chart shows wire gauges to be used if no less than a .5 volt drop is accepted.
Cable size calculation takes into account terminal connection resistance.
When running power wires to the amp, keep them as far away from the RCA wires (see alternator noise section for more info), ideally on the other side of the car. It is OK to run the turn-on wire from the radio along with RCA’s, since it carries very little current.
Amplifiers produce a lot of heat and need to receive plenty of fresh air. If the amplifier is to be mounted under a seat, upside down, in a rack or enclosed, a fan or two might need to be used to increase air flow.
To avoid noise problems, it is good practice to mount the amplifier itself to a piece of wood or other non-conducting material. That way the only ground it gets is from the ground wire and not the mounting screws.