Accessories, Care & Maintenance

What Is A Guitar Load Box? – Load Boxes Explained

Written By :Andrew Siemon

In order to run a tube amplifier, you need an output for all the energy that the amp creates. In the case that you don’t have a speaker cabinet or some other piece of gear that acts as an output for that power, there’s a good chance you might cause serious damage to your amp head. This is where a Load Box comes in handy. You’re probably wondering what this is.

Essentially, a load box is a device that acts as an interface in which the energy generated by a tube amplifier can be expressed, without using a speaker cabinet. An amp head creates a lot of energy and power, and there needs to be a location for that energy to go. The device “loads” the amplifier.

Normally, a speaker cabinet is what we use to “load” the amplifier’s electrical current. The load box acts as a replacement for the speaker cabinet.

Explained in another way, a load box takes the power and electrical signal from the amplifier head and decreases it down to a safe level – also called “line level” – that way the signal can be expressed through a system without damaging the amplifier head. 

The load box provides a location with matching electrical properties that the amplifier head expects to labor under. This is why it’s called a “load box,” because the device is literally loading the electrical current.

There is a lot of power, energy, or electrical signal from the amplifier. And this power/signal needs a place to go. A cabinet speaker system is a place for this power to exist. It’s called the load because it’s the place where this electrical power can go and express itself. This isn’t to be confused with an attenuator.

Attenuation just means we’re decreasing the power of an electrical signal. For instance, if you attenuate a certain frequency when adjusting the Channel EQ on an instrument track, you’re literally decreasing the signal. 

You may have heard a phrase like, “attenuate 300Hz by 3dB.” This means we’re decreasing the frequency 300Hz by 3dB. This looks like what we can see in the image below: 

An attenuator absorbs some of the power from the amp between the speaker and the amp head. It acts as a volume control. This is different from a load box in the following way.

A load box packages all of the power created by a tube amplifier and makes it so this energy can be safely communicated through a computer, a PA system, or some other recording device.

A consequence of this is that you’re able to use a load-box in order to transfer the power of an amplifier head, that way we can then run that signal into a computer for recording, all without a speaker system that would normally handle the amp’s electrical signal. 

Additionally, tube amplifiers – and many other forms of audio equipment – work best after they’ve been turned on for a certain amount of time and at a certain volume. 

When I first started using a tube amplifier and a speaker cabinet, I was a bit annoyed that you would have to run the amplifier at a certain volume/gain in order to get the best sounds out of it. 

For instance, if you don’t have a load box, you have to turn on the amplifier head with the cabinet connected and it has to be turned up nice and loud in order for it to reach its maximum potential, which means you’re going to upset a lot of people around you who don’t necessarily want to listen to your playing. 

This is also another useful feature of the Load Box like this one which is probably the most popular.

The Load Box is able to handle the power of the amplifier, process it, and then send it in to a computer for recording, practicing, or for whatever else you need. 

This means that you can play the guitar through your amp/cabinet combo at its maximum potential, without annoying everyone around you.

Now that we’ve unpacked what it means in simple terms, we’ll move on to a more specific understanding and explanation. 

How A Load Box Works With An Amplifier

A valve amplifier, also known as a tube amplifier, needs a load (a speaker system) in order for it to function normally without causing damage. 

A load, in more scientific terminology, is a set of electrical properties which the amplifier head is expecting to see. 

The load is a place for the electrical signals to go. These electrical signals or electrical properties are called “impedance.” Typically, a load is commonly thought of as a cabinet speaker system. 

Speaker systems, output transformers, and tube amplifiers communicate with one another through a set of changing electrical properties. 

A change in energy in the tube amplifier and output transformer will be expressed through the speaker system. 

The ongoing conversation between the tube amplifier, the output transformer, and the speaker system, is part of what makes the amp/cab combo so special.

It generates that coveted sound that gearheads always talk about.

This energy transfer doesn’t exist in solid-state amplifiers, and it’s one of the reasons why people consider solid-state amplifiers as inferior to valve amps. 

What Happens If I Don’t Have A Load? 

If there is no load, or in other words, a place for the electrical signals to labour under, the amplifier’s output transformer and valves will see an infinite impedance, which means there will be a massive spike in voltage as the signal is sent through the amplifier. 

A massive spike in voltage and power is what can damage the amplifier’s inner components including the output transformer. There are a number of settings in which a guitar player may want to use their amplifier but without a very noisy speaker system. 

For instance, you may want to run the amplifier into the system in a concert venue, or into the desk of a recording studio, without the speaker system. In the aforementioned circumstances, we need to have a dummy load, or a load box, which is a place for the electrical signal to exist. 

The load box behaves similarly to a speaker system in terms of being able to handle all of the electrical signals, but without generating a ton of noise. In most tube amplifiers nowadays, there is actually an emergency setting built into the amplifier which protects it from being permanently damaged in the case that you don’t have a speaker system connected to the amplifier head. 

However, this isn’t always the case, and it’s important to ensure that you always have a load connected to the amplifier, that way that the amplifier’s signals can be safely communicated through a system of some sort where there is no risk of damage. 

The term, “load box,” is a device that embeds any electronic signal. The term, “impedance,” as I mentioned above, is the word we use to explain the power that’s being created by the amplifier, and we use the measurement, “ohms,” to designate and define this power. 

For instance, if you have an 8-Ohm load box, it has to be connected to the 8-Ohm speaker output of the amplifier. 

The power that is sent to the load box or the speaker system is transformed into heat, so there are certain recommendations to follow to ensure that the load box or speaker system can cool down and isn’t at risk of being destroyed. 

In other words, the load box can take all of the heat – which is the power generated by the amp – and this replaces the speaker cabinet. A load box is also used to test amplifiers silently.

YouTube Video Tutorial

What Is A Guitar Load Box? - Load Boxes Explained


There is a lot of information to unpack here.

In the simplest terms possible, a load box is a device that handles the electrical current from an amplifier head so it can be safely communicated through an external system of some sort, like a PA or a computer.

It replaces the speaker cabinet and makes it so that you can use our amplifier head at its maximum potential without creating a lot of noise, and without a speaker system.

Andrew Siemon is the principal creator for, a website entirely devoted to all things guitar. From repairs, music theory, chords, and improvisation, to recording at home. I've been doing this for 20 years and I've got another 50 in me.

Leave a Comment