What Is an Amplifier?
An amplifier is an electronic device that increases the strength of an audio signal so it can power speakers and produce sound at audible volume levels.
In a hi-fi system, the amplifier sits between your source device (such as a CD player, streamer or turntable) and your speakers.
Why do you need an amplifier?
Most audio source devices output a low-level signal that is too weak to drive speakers directly.
The amplifier boosts this signal, providing enough electrical power to move the speaker drivers and create sound.
How does an amplifier work?
An amplifier takes a small input signal and increases its voltage and current without changing the original audio content.
- The source sends a low-level signal to the amplifier.
- The amplifier increases the signal strength.
- The amplified signal powers the speakers.
The goal is to increase volume while maintaining clarity and low distortion.
Types of amplifiers
Integrated amplifier
Combines a preamplifier and power amplifier in one unit. Common in stereo hi-fi systems.
Power amplifier
Provides only signal amplification. Requires a separate preamplifier.
Preamplifier
Controls volume and input selection but does not directly power speakers.
AV receiver
A multi-channel amplifier designed for home cinema systems.
Amplifier classes explained
Class A
Known for continuous output operation and high heat generation.
Class AB
A combination of Class A and Class B efficiency. Common in many hi-fi amplifiers.
Class D
Highly efficient switching amplification. Common in modern compact and streaming amplifiers.
Amplifier power (watts)
Amplifier power is measured in watts.
Higher wattage generally allows an amplifier to drive speakers at louder volumes or control more demanding speaker loads.
However, matching amplifier power to speaker sensitivity and impedance is important.
Do all speakers need an amplifier?
Yes — but not always separately.
Passive speakers require an external amplifier.
Active speakers have built-in amplification.
Frequently Asked Questions
What does an amplifier actually do?
It increases the strength of an audio signal so that speakers can produce audible sound.
Is an amplifier the same as a receiver?
A receiver includes amplification plus additional features such as radio tuners or multi-channel processing.
Do headphones need an amplifier?
Some headphones can run from phones or laptops. Higher-impedance models may benefit from a dedicated headphone amplifier.
In simple terms
An amplifier makes your audio signal strong enough to power speakers and produce sound at usable volume levels.