The average amplifier can get so loud that, even when the volume is set below halfway, the neighbours already start banging on the walls. What an attenuator or power attenuator does is lower the output volume of your amp while retaining the full sound and character of the tone.
Audio & Power Attenuators
A guitar attenuator (also known as an audio or power attenuator) is a handy device that keeps the character of your guitar amplifier fully intact, just at a much lower volume. Attenuators are handy tools whether rehearsing at home or recording in a studio since, if you've ever heard a valve amplifier with an output over 20 Watts with the volume pushed all the way up to 10, then you know it's really, really loud. However, simply turning the volume down isn't really the solution, because the beauty of a valve amplifier is the rich sound of hot overdriven valves - which traditionally, you can only get when the volume is cranked up. By placing a power attenuator between the amplifier head and the speaker cabinet via standard speaker cables, you can lower the volume but keep quality of sound. The unit absorbs part of the signal and converts it into waste heat - otherwise known as a 'power soak'. The amount of signal that's absorbed is set by a switch on the attenuator. The amount of Watts a unit is able to handle will differ from model to model. For example, a 100 Watt amplifier shouldn't be linked to a 50 Watt attenuator, but a 100 Watt attenuator can handle a 50 Watt amplifier. You'll also need to check that the impedance of your amp and attenuator match up.
Voltage/Variac Attenuator Circuits
Another method of attenuation is via a variac circuit. Variac attenuators influence the voltage that's sent through to the power amp valves to result in natural overdrive at a lower volume. However, variac attenuators can have an affect on the lifespan of your amplifier at lower volumes, and can be less effective than power-soak attenuators. Some Variacs can also make a valve amp sound a bit darker.
Built-In Attenuators
More and more modern amplifiers come with an attenuator built in, but depending on the model, use different methods of attenuation. So, you can get amplifiers with an integrated attenuator with a wattage switch, so you can flip the output down from 50 Watts to just 5 Watts, or even as low as 0.1 Watt. There are also amplifiers with an attenuator that's adjusted via a standard rotary pot based on the output volume. Some amplifiers will also feature attenuators equipped with a 'reactive load' (read more about this below).
Attenuators: Reactive Load or Load Boxes
Basically, a reactive load allows an amplifier head to function without needing to hook up a speaker cabinet. To avoid causing the amp damage, a speaker always needs to be plugged in whenever the guitar amplifier is switched on - unless the amp features a reactive load circuit. Attenuators with a built-in reactive load circuit support direct connection to gear like an audio interface or PC so that the sound of the amp can be coupled with speaker simulations, and so you can play in near-silence. External devices designed to add a reactive load to the chain are called load boxes. While the attenuator's job is to lower the output volume, the job of the load box is to remove the need to plug in a speaker.
Attenuators: Cab Sim/Speaker Simulation
Some reactive load attenuators also come with a built-in speaker simulator. These sort of attenuators often include a headphone output, and thanks to the built-in speaker simulation, you can connect the signal directly to an audio interface and still get the full sound of an amp stack. Of course, you can also get separate external speaker simulators.
Note:
Never set up a guitar amplifier head without hooking up a speaker cabinet or load box first, otherwise you risk causing irreparable damage to your amp. To avoid causing damage when setting the attenuator, always go from a high volume setting to a low volume setting.
Frequently Asked Questions About Attenuators
What's an attenuator?
An attenuator is a device that's able to lower the volume of a guitar amplifier without affecting the quality of sound and overdrive level. The idea is that you can get the same raw sound of an amp at full volume but at a much lower volume - perfect for rehearsing at home.
How do you set up an attenuator?
Most attenuators are placed between the amplifier and speaker cabinet. You then use the attenuator to adjust the volume, while the setting of your guitar amp and pedals still dictate the guitar sound.
Can you get guitar amplifiers with a built-in attenuator?
There are loads of guitar amplifiers that come with a built-in attenuator these days. Some will reduce the wattage and are controlled via a switch fitted on the amp, while some built-in attenuators lower the output volume and are controlled via a rotary pot.
Which attenuator should I get?
When picking out an attenuator, you need to check that the model is able to handle your amplifier. For example: a 50 Watt attenuator isn't able to handle a 100 Watt amp, but a 100 Watt attenuator is able to handle a 50 Watt amp.
