You MUST run a dedicated power cable to your amplifier. Do not try to take the feed from somewhere else in your car, as it would not be designed to handle the power.
The earth lead should be as short as possible to minimise ground loop isolation, which will cause disturbance. The best place to connect the earth is next to the amplifier, on the boot floor, or to a seatbelt mount. It’s important that the paint is cleaned off of the metal for the best possible connection. (A cars body is negatively earthed this is why it can be used for the negative terminal, also make sure the power cables do not short out against the car body when you are fitting them)
You will need to install an inline fuse to your power cable. If the cable were to fall out of the amp it would short out against the car body, and either melt the wire, destroy the battery or cause a fire. Also it is possible for the electronic safety fuse inside of an amp to break if it is triggered too often, and this will result in the amp catching on fire. This is why you need to have an inline fuse so it can stop this from happening. We recommend that this fuse is slightly higher than what the amplifiers can draw, but not significantly higher. If a fuse keeps blowing, it’s for a reason. Don’t just install a bigger one, as eventually something will blow other than the fuse.
Running the power cable:
This cable must be ran from your battery, which means you need to find a place to feed it into the car. There usually won't be one, so all you need to do is drill a small hole in the bulkhead. It will need a rubber bung around this hole to prevent it from cutting into the insulation of the wire. DO NOT just drill a random hole. There will usually be brake pipes opposite your hole, it's sods law. Check each side, and even if you are sure there is nothing in the way drill very slowly and do not push hard. If you push too hard you risk ramming it into something important on the other side when you realise you're not drilling where you thouhgt you were.
You will have to drill this from inside the car, as there will not be room behind the engine. If you are really fussy you can put a bit of paint around this hole to stop it from rusting.
Once your cable is inside the car you need to run it under the carpet. The best way to do this is along the side of the door rubbers. If you pull these off the carpet will usually lift up, or it may also have some clips. Push the wire down so that the carpet can go down flush again.
Do this on the opposite side for your RCA leads. (RCA lead is the same as a phono lead)
Also you need to run an ignition live to your amplifier, so that it turns on when you turn your cars' ignition on. This will not use much power, so the cable does not have to be overly thick. To find this:
Disconnect the iso plug from your radio.
Test for permanent lives,
Turn on the ignition,
There should now be another source of live.
This is the ignition live that you will need to feed back to your amplifier.
RCA leads.
These will also run from your head unit, and carry the signals to the amplifier.
It is important that these are run down a separate side of the car to the power cable.
When a current runs through a wire, a magnet field is produced around it. If the wires are next to each other these sensitive RCA leads will pick up interference, and this will then be amplified to your speakers. Common signs of this are that there is a buzzing that increases when you rev your engine. To eliminate the buzzing try moving the wires away from each other. If unsuccessful the next step would be to install a ground loop isolator. This does not stop the problem, and only masks it.
Is your buzzing still there?
Speaker cables:
Like everything if you don’t use a quality product the output will have a low quality.
Use new wires to all speakers, and quite thick wire to feed your subs.
How thick does my amp power cable need to be?
If you are sending a lot of current to your amp, you will need a thick cable.
The scale that cable is measured in is backwards. A 4AWG cable is a lot thicker than a 16AWG cable. In the AWG scale (American wire gauge) each larger size is about 26% larger than the previous one.
You can use this as a rough guide to how thick your cable needs to be. Ultimately the quality of the copper used determines the maximum useable current:
Gauge |
Diameter |
Area of wire |
Max Current |
|
Inches |
(mm) |
(mm) |
currentAmps |
|
OOOO |
0.460 |
11.684 |
107.16 |
302 |
OOO |
0.410 |
10.404 |
84.97 |
239 |
OO |
0.365 |
9.266 |
67.40 |
190 |
0 |
0.325 |
8.252 |
53.46 |
150 |
1 |
0.289 |
7.348 |
42.39 |
119 |
2 |
0.258 |
6.543 |
33.61 |
94 |
3 |
0.229 |
5.827 |
26.65 |
75 |
4 |
0.204 |
5.189 |
21.14 |
60 |
5 |
0.182 |
4.620 |
16.76 |
47 |
6 |
0.162 |
4.115 |
13.29 |
37 |
7 |
0.144 |
3.665 |
10.55 |
30 |
8 |
0.129 |
3.264 |
8.36 |
24 |
9 |
0.114 |
2.906 |
6.63 |
19 |
10 |
0.102 |
2.588 |
5.26 |
15 |
11 |
0.091 |
2.304 |
4.17 |
12 |
12 |
0.081 |
2.052 |
3.31 |
9.3 |
13 |
0.072 |
1.829 |
2.63 |
7.4 |
14 |
0.064 |
1.628 |
2.08 |
5.9 |
15 |
0.057 |
1.450 |
1.65 |
4.7 |
16 |
0.051 |
1.290 |
1.31 |
3.7 |
The average user will need around 4AWG cable.
