What is a load box?

A load box basically replaces your guitar cabinet and prevents your beloved amp to break. To understand how a load box work, let us go back one step.

Watts, ohms, how does it all relate?

A guitar amplifier is a two-way system:

an active part that produces and delivers electrical energy: the amp
a passive part that receives the electrical energy and changes it to sound: the cabinet with its speaker.

If the active part does not have a recipient, the amount of voltage will rise abruptly until a part gives way. In an amp, it can be the fuse, the power tubes or the output transformer that breaks.

With a cabinet, the amp is limited to its maximum power delivery through the impedance of the cabinet (for example 100w/8 ohms) In theory, saying my amp is 100w does not make much sense, but this would not be the first or only thing we say without any sense. We should say “my amp is 100w through my 8-ohm speaker”.

How to use a load box?

This is where the load box comes to light. It gives the amp a recipient for the energy it delivers so it does not destroy tubes, output transformer when turned on, through a designated impedance (4, 8, 16 Ohms). It takes the energy sent by the amp and transforms all or part of it in heat, and is able to send a line or microphone level signal to a sound card or a mixing desk.

A load box has many advantages:

you can record silently to a soundcard or DAW
you can attenuate the sound level going to the cab if your load box is equipped with an attenuator system
you can play at every hour of the day and night
you can leave your cab at home for a gig, and send the signal of the load box to the mixing desk

Choosing a load box will then come down to what you are looking for: attenuation, silence with analog simulation, silence with digital simulation, reactive or resistive load, reamping.