glass electric fuse

What Size of Fuse Should I Use for My Amp: the basics

One of the less often asked questions when it comes to car audio systems is what size of fuse should I use for my amp? Since the size of the fuse in the amp does not directly impact sound quality, there can be a tendency to overlook its significance.

But to overlook the importance of fuse size in car amps can prove to be really dangerous as you’ll see below. Here you will learn about the importance of fuses and their different sizes and types.

What is a fuse used for?

A fuse is generally inserted into an electrical circuit to protect the electrical device (amplifier) from the power source.

The amp manufacturer specifies a fuse that is rated to break the electrical circuit before damage is inflicted on the device. This will break the circuit if the electronic device fails in some way (since such devices may pull excessive current when they fail).

In this article, we will focus on the fuse used in car amps and discuss why they are so important for the car and amplifiers safety and performance.

As most cars come from the factory without an external amplifier fitted, then you need to wire it into power separately. This means you will need some type of fuse to protect your amp.

Why should I put a fuse before my amp?

When running a power wire for your new amp, you should always wire in an inline fuse before the amplifier. If you run this wire without a fuse and your amp has an electrical fault it can cause the power wire to earth against the car body.

This will cause the power wire to overheat and melt the plastic covering and in some cases cause your car to go on fire. Power wires can also rub against a part of the car and wear away the protective covering resulting in the same outcome.

What size fuse holder should I use for my amp?

car automotive fuse replacement from fuse box
Removing an automotive fuse from the fuse box

Apart from placing your fuse in the right position, it’s also very important that you use the right size fuse. For instance, a fuse that’s too small will blow during normal operation. Similarly, on the other hand, a fuse that’s too big could end up not breaking the circuit with component failure causing an electrical fire.

The correct size of fuse to use depends on the amp you are wiring. If your amp has an internal fuse, then your inline car amp fuse should be a bit larger. For instance, if your amp has an internal 20 amp fuse, then you should go for a 25 or 30 amp inline fuse.

Suppose you have two amps. In that case, you should add those numbers together to figure out the right size for your inline fuse. For instance, if you have two 20 amp internal fuses, then the size of your inline fuse should be more than 40 amps. This equation gives you a little more room without exposing yourself to a dangerous situation.

For amplifiers that don’t have internal fuses, you’ll need to check the power ratings of your amp. Based on this info you should determine the perfect size for your inline car amp fuse.

Sometimes you may have multiple amps which don’t have internal fuses.  In these cases, you should use a fused distribution block. A fused distribution block will protect multiple amps and other related components.

What type of fuse should I use?

Once you work out the size of a fuse for your amp, the next question is the type of fuse to go for. There are a number of different types of fuses, I will summarise below:

Types of Fuses:

Automotive fuse

The internal fuses of most amps are mostly some type of automotive fuse. These fuses are of the same type of fuse that is used elsewhere in your car and other audio components. These are flat with two prongs. For instance, the head unit of the car sound system might also use this same fuse.

Inline fuse

You can use this same type of blade fuse when you install an inline fuse. The fuse is installed in the fuse holder itself. The fuse is then connected in line with the amp power line.

In-line barrel fuse

Another option is to go for an in-line barrel fuse. This type also uses a fuse holder which you have to install in line with the power wire. It takes the form of a clear or translucent plastic tube, one that holds a barrel fuse.

MulWark have a great assortment of fuses in one box set – take a look and see if they are a fit for you.

What size of fuse holder should I use for my amp?

inline barrel fuse beside a speaker
An inline fuse beside the speaker

The size of the fuse is more important than the type you are using. Regardless of the type of fuse you choose, it’s important that you select a fuse that meets (or exceeds) the rating of the fuse that you are planning to install. For instance, if you choose to go for a 30 amp inline fuse, don’t install a fuse holder that’s rated for 25 amps only.


Selecting the correct size of a fuse is an integral part of the car stereo system, especially when it comes to your safety. We also know that there are different types of fuses for different applications. And these fuses come in different sizes.

Choosing the size of the fuse depends on the size and power of your amp. All amps will have manufacturer specifications for the size of the fuse to be fitted. Even if the manufacturer has a fuse built into the amp it is always better to have your own in-line fuse wired before the amp. Any questions- drop me an email- or leave in the comments below. Thanks!

34 thoughts on “What Size of Fuse Should I Use for My Amp: the basics”

  1. When someone writes an post he/she keeps the
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  2. Choosing the correct fuse for you new audio system is very important and falls into 2 categories. The main fuse is mounted next to the batteries positive terminal. It stores voltage but the alternator does double duty buy suppling the vehicle with enough amperage to run all of the systems (If On At The Same Time) but to recharge the battery.
    The stereo, amps, digital signal processor all add up. If purchased new, info regarding fuse size comes with the paperwork. Add item #1, #2, #3 together and install a main fuse the is equal to or just below, as no one runs all item wide open a max. Electronic consume amperage. The higher the amp requirement is, the larger the wire inside the PVC cover should be. If purchased used or came with the vehicles, each components needs to be measured by an amp clamp. This goes around the B+ cable while the device is on and temporarily turned to maximum output. Amp clamp are reasonably priced and cheap insurance. Sears, Radio Shack, Harbor Freight and home improvement stores sell them and have a digital readout and possibly a “Hold” button. This allows you to measure each, push hold, remove from the vehicle & right is down. A distribution block should be installed with the correct size fuse for each. Check charts online for wire size, amps + length. The longer the cable, higher amps required will tell you cable size. Please install it from the distribution block forward to the battery B+ terminal allow room for a single main that equals all measured devices. Many will argue but if 85 is your total, use an 80 amp fuse. This does not reduce sound, cause distortion or creates a bottle-neck. It is safety. The fuse the a thermal sensing device, not an amperage device. It is precision device, made to open at a temperature that is very close to the circuits amperage usage. The popular fuse called the “Mini ANL” is popular because it’s a smaller size and works the same as bigger fuses with same rating. They attach in a holder with hex head wrenches called “Allen” wrenches and hold well. Dielectric grease is an excellent $5/$6 choice and sold in home improvement stores in automotive. This covers metal parts that carry electricity and looks like vasoline, but keeps humidity, battery fumes, water and even finger oils from corroding the metal parts.
    But measure with an amp clamp, auto techs all have one that measures DC or direct current and readout on a dial or gauge. A chart for length with a tape measure, main fuse next to battery, properly ran cable away from heat, sharp metal, pinch points like hood or door, thru a rubber boot and cable ties sold everywhere. A little time, some research, purchases, and install safely. No one want smoke in the car, while sitting still or driving down the road. Cutting thru an electrical wire / cable is the worst thing ever. Many airplanes had crashed in the 50’s & 60’s because a wire rubbed on sharp metal. You invest a couple of hundred to well over a thousand dollars, spend $45 for an amp clamp, dielectric grease, rubber grommets, correct fuses and the time is takes to look good and sound good! Play it safe as your friend, relative or mom or dad may never turn on you music, but can still get hurt! Be the smart one, do it right!

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