What Is a Speaker Amplifier (And Do You Need One)?

Sonos Amp placed on a bookshelf

A speaker amplifier, or “amp” for short, is an electronic device that boosts an audio signal’s power to a level that can be heard through speakers or headphones. Some form of a speaker amp is necessary regardless of whether you’re playing music from a turntable, a laptop, or a CD player. But that doesn’t necessarily mean you’ll need to invest in a standalone amp, as many amps these days are built into the speakers themselves.

In this guide, we’ll review the basics of speaker amplification and help you decide if you need an amp for your setup.

What is a speaker amp?

To explain the job of a speaker amp within the context of a home audio setup, let’s start with an example of what an audio signal can sound like without amplification.

If you play a vinyl record before connecting or turning on your speakers, you’ll notice a faint sound of music emanating from the turntable itself. Sometimes referred to as “needle talk," this sound is actually the vibration of your record player’s stylus as it runs along the record’s groove. Without amplification, this vibration can sound high-pitched and whisper-quiet. Before you can enjoy it as music, it must be converted into an electrical signal and made louder. Much louder.

A speaker amp is the device responsible for boosting — or amplifying — this electrical signal so that it can be heard from your speakers as music. Think of an amp as the muscle of your audio setup, taking a weak signal from your audio device and pumping it up to a level that can drive your speakers or headphones.

So, the speaker amplifier’s primary job is to increase the volume of your audio. But an amp has other responsibilities, too. It helps to regulate the level of power supplied to your speakers so they don’t get pushed beyond their limits and damaged. An amp can even shape your sound in various ways, from reducing distortion to adjusting the audio signal’s tone and frequency to suit your preferences (a process known as equalization, or EQ).

How does an amplifier work?

A speaker amplifier works by taking a weak electrical signal from your musical source — like a turntable or CD player — and increasing its amplitude. Amplitude is a measurement of a sound wave’s strength, with higher amplitude sound waves creating louder sounds and lower amplitude sound waves creating quieter sounds.

Once the audio signal is amplified, the amp sends it to the speakers. The powered signal then creates vibrations in the speaker cone, which generate sound waves that your ears hear as music.

Most amps come with controls that allow you to fine-tune the sound and adjust the gain, which refers to how much the audio signal is boosted before it’s sent to the speakers. More gain means more volume, but too much gain can distort the sound quality and result in a phenomenon called “clipping,” whereby the tops and bottoms of the sound wave are chopped off because the amp can’t handle the full breadth of the signal. Not only can this sound unpleasant, but it can also damage your speakers by pushing them beyond their maximum capacity.

Fortunately, most high-quality amplifiers have built-in protections to prevent any damage resulting from excessive gain. These amps may limit the amount of power sent to the speakers to avoid issues like overheating and tearing of the speaker cone.

One point to underline here is that, regardless of its type, an amp relies on electricity to work, so it will need to be either plugged into an electrical outlet or powered by a battery.

Back view of an Amp placed on a shelf
Amp placed next to a turntable on a shelf

When do you need a speaker amp?

The bottom line is that you will always need some kind of amp to listen to music or watch movies with your home theater system. But if you’re looking for the amp in your home audio setup and can’t find it, there may be a good reason.

While an amp is always a necessary component, it isn’t always a separate component. Most Sonos speakers, for example, include a built-in amp so they’re ready to play right out of the box. These are called active speakers, or powered speakers, because they actively generate their own power and don’t require an external amp.

Speakers without built-in amplifiers are commonly referred to as passive speakers. These speaker types are often used in architectural setups, where the speakers are discreetly installed into a room’s walls or ceiling. Passive speakers require power from an external amp, like our WiFi-enabled Sonos Amp.

Whether you go with active or passive speakers will largely depend on your audio setup and your willingness to pair your speakers with an external amplifier. A multiroom audio setup with in-ceiling or in-wall speakers will likely require a separate amp for power. But you can also achieve phenomenally realistic surround sound with, say, a pair of Sonos Era 300 speakers, each of which includes six class-D digital amplifiers to power your sound experience.

How Sonos Amp can help

If you’re set on including architectural or outdoor speakers in your home audio system, you’ll need a high-quality amplifier that can deliver enough power for multiroom listening. That’s where Sonos Amp can help. With 125 watts per channel, it has more than enough power to produce high volumes with clear, undistorted sound. Whether your goal is a hi-fi listening setup or a smart home with seamless control, Amp is all the amp you’ll ever need.

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