Guide to Installing 2 Car Amplifiers Together

Last Updated on December 4, 2023 by CarAudioHunt

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Guess we all are tired of listening to less boom and more blah from our car audio system. Even a single amplifier can't support all its potential with all the subwoofers and tweeters. So, it is high time to double up on the power and reach the next level.

Here we are, your supervisors, presenting the most effective method of installing 2 car amps together and unlocking the symphony of sound that'll make your ride rock and roll.

From the amplifier’s specifications, you come to know the wattage. But that's not enough to understand how much current the two amplifiers will draw out from the battery.

Suppose you have two amplifiers of 1200 watts and 800 watts. The current they will require:

I = P/V [Current= I]; [Watt = P]; [Voltage=V]

= (1200+800)/ 13 [the system voltage for the Car amplifier is 12 - 14.4]

~ 148 amps

Yet, it’s not the actual current flow for the power cable of car amplifiers. No amplifiers are 100% efficient. They require more current than what they put out. Maximum amplifiers are 80% efficient. So, here is the new value of current for 80% efficient amplifiers.

I = 148/.80 [.8 because it’s 80% efficient]

= 185 amps

To put it simply, if you desire constant music at its loudest, you might need close to 185 amperes. But music isn't consistent, and the intensity of the music goes up and down continuously. That's why amplifiers won't draw 185 amperes from the battery at a constant rate. Amplifiers consume roughly 50% of their maximum input current. Here, the amplifiers are likely to consume 92.5 amperes (50% of 185 amperes).

To determine the exact wire gauge for the amplifiers, calculate the exact input amperage range for two amplifiers and consider the length (distance between battery and amplifiers). As reported by our calculation above, the input current flow is 92.5 amperes, and the length between the bonnet and the trunk is 14.7 feet (Almost equal to the average car length). According to the amplifier’s wire gauge chart (the chart is available to any car audio-related stores and the internet), the input current range of 85-105 ampere requires 4-gauge wire (power and ground) for a typical 14.7 feet long car.

Equipment for Hooking Up Two Amplifiers

Hooking up two amps in a car has almost all the kits typical to single amplifier installation. but you will require some additional kits for dual amps. Let's explore every kits you'll need:

Equipment for Hooking Up Two Amplifiers

1. Cables

You already know about the use of power and ground cable for completing the electrical connection. Then you will need 2 good quality RCA cables to carry audio signal from head unit. Don’t forget to grab remote leading wire for turning on and off the amplifiers and standard speaker wires to connect the speakers and subwoofer.

2. Powerful In-line fuse

Typically, calculating the size of the In-line fuse depends on the maximum power input (185 amperage in this case) for both amplifiers.

But that is applicable when you use a power and ground wire, thinking of maximum power input for amplifiers. But there is 50% power input for amplifiers (92.5 amperes), and the 4-gauge wire of 14.7 feet supports up to 105 amperes. So, anything more than 105 amperes will likely burn the power cable. That’s why you should get an inline fuse that’s not more than 105 amperes.

3. Distribution Block

As the amplifiers will draw power from the battery to a single power cable, there has to be a point where the power will be distributed. The distribution block works like a power splitter here, takes power from the battery and gives it to the amplifiers.

In contrast, the two ground cables from the amplifiers will meet in the distribution block from amplifiers, and then a single cable will do the grounding. Here, you need 2-way 4-gauge distribution block for 4 gauge of power and ground cables.

4. Transmitter

For the remote turn-on cable, the signal strength from both the factory head unit and after-market head is not strong enough to turn on the amps. And it happens mostly when two powerful amps are running simultaneously. A transmitter will make the signal stronger enough for both of the amps.

Hooking Up Two car Amplifiers with a Distribution Block

After collecting all the kits for installation, now that you are ready to hook up with our six-step guide, let's go into the steps:

2 amplifiers wiring diagram

Step 1: Connecting with In-Line Fuse

First, disconnecting the negative terminal of the battery, you should mount the in-line fuse holder and the inline fuse near the battery. Split the power cable using a wire trim and connect one end with the in-line fuse. It's better to add a ring terminal on the other end of the power cable and connect it with the positive terminal of the battery.

Now, you must attach the remaining power cable with the output end of the in-line fuse and run the cable through the firewall grommet to the location where you have mounted the amplifiers.

Step 2: Input Power wire into the Distribution Block and Get two Different Power Connections

You’ll require a distribution block to split the power for both amplifiers. After mounting the distribution block at the nearest location to amplifiers, connect each amplifier with a power cable from the distribution block.

Remember, the distribution block can distribute the power non-equally. So, ensure the maximum power output in the distribution block is connected to the high power-consuming amplifier. The lower one is connected to a low-power consuming amplifier between two amplifiers.

Step 3: Adding Distribution Block for Ground Wires

Just like power connections, use two (same gauge as power cable) ground cables from two amplifiers and then connect them to a distribution block. The output wire from the distribution block will be attached to the metal nut.

Step 4: Connect the RCA Cables

The conventional way to connect the RCA cables to two amplifiers is by pre-amp pass-through (output) connection. It means the first amplifier will have RCA input connection from the head unit. Now, you have to take another RCA cable from the same amplifier's RCA output and plug it into the next amplifier's RCA input.

In modern vehicles, the head unit has several preamp outputs for hooking up at least two amplifiers. In this case, connect the two RCA cables from the head unit to the amplifiers. Also, using the Y splitters help to connect two amplifiers with dead units by one RCA cable.

Step 5: Integrating a Transmitter for Strong Signal

As there is only two amplifiers, most experts suggest having the remote lead connection through a series of wiring. It means you will run the remote wire from the head unit to the 1st amplifier and the 1st amplifier to 2nd amplifier.

But for high-end amplifiers, the series wiring can't turn on both amplifiers for the weaker signal of the head unit. That's where the transmitter helps, you have to attach the remote wire from the head unit with the transmitter and it will transmit strong signals to both the amplifiers.

Step 6: Connect the Speaker Wires

Now, wire the amplifiers with speakers, subwoofers and tweeters. If you love bass, ensure powerful subwoofers are connected to the powerful amplifiers. Connect the positive speaker terminal to the positive amp terminal and do the same for negative terminals.

Finally, when all the wirings have completed, double-check them again using our above diagram. You can now connect the unattached negative terminal and power up the amps.


Once you know the basics of wiring two amps, you can do various sound improvements, like one amplifier for bass and another for highs. As you become more familiar with the setup, adding other modifications won't confuse you.

Hopefully, this guide will help to do the practical installation effortlessly.

Related Guides You May Read:

  • Installing 3 Amps in a Car Together
  • Car Amplifier Buying Considerations
  • Guide for the Amp Settings for Bass in Car

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