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An amplifier takes a small signal from a source and makes it strong enough to drive speakers. Most amplifiers do two jobs: a preamplifier section selects inputs and controls volume, and a power amplifier section provides the muscle. How those jobs are packaged defines the main types.
Types of amplifiers
Integrated amplifier
Preamp and power amp in one chassis. The standard choice for stereo hi-fi. Many now include DACs, phono stages and streaming.
Preamp + power amp
Two (or more) boxes. More flexibility, isolation and upgrade options — at higher cost and complexity.
Stereo receiver
An integrated amp with a built-in radio tuner (FM/AM, sometimes DAB or internet radio).
AV receiver (AVR)
Multichannel amp with HDMI switching, surround decoding (Dolby, DTS) and room correction.
Streaming amplifier
Compact amp with Wi-Fi streaming, often HDMI ARC. Just add passive speakers for a complete system.
Headphone amplifier
Designed to drive headphones cleanly, especially high-impedance or low-sensitivity models.
Phono preamp
Boosts and equalises a turntable cartridge’s signal to line level.
Mini / desktop amp
Small, efficient Class D amps for desktop or bedroom systems at low cost.
Tube vs solid-state
| Tube (valve) | Solid-state (transistor) | |
|---|---|---|
| Character | Often described as warm, rich and liquid; distorts more gently when overdriven | Typically neutral, precise, with strong control over the speaker |
| Power | Usually lower output; best with efficient speakers | Wide range, from a few watts to hundreds |
| Maintenance | Tubes wear and need replacing; run hot | Largely maintenance-free |
| Cost per watt | Higher | Lower |
Hybrid amplifiers use a tube preamp stage with a solid-state power stage, aiming for some tube character with solid-state power and reliability.
Amplifier classes: A, AB, D and more
The “class” describes how the output transistors (or tubes) operate. It affects efficiency, heat and size — not directly whether an amp sounds “good”.
| Class | How it works | Efficiency | Typical use |
|---|---|---|---|
| Class A | Output devices conduct all the time | Very low — runs hot | Low-power high-end amps, headphone amps |
| Class AB | Works like Class A at low levels, then shares the load between devices | Moderate | Most traditional hi-fi amplifiers and receivers |
| Class D | Switches rapidly on and off (PWM); filtered to recover audio | Very high — cool and compact | Powered speakers, soundbars, subwoofers, modern hi-fi |
| Class G / H | Changes supply voltage depending on signal | Higher than AB | Pro audio, some AV receivers |
Class D’s early reputation for harsh sound is outdated. Modern Class D modules measure extremely well and power many excellent products.
How much power do you need?
Less than most people think. Every +3 dB of loudness needs roughly double the power, and +10 dB (which sounds about twice as loud) needs ten times the power. What really decides it:
- Speaker sensitivity: a 90 dB speaker needs about half the power of an 87 dB speaker for the same volume.
- Room size and listening distance.
- How loud you listen and how dynamic your music is.
For typical rooms and speakers, 30–100 W per channel of clean, continuous power is plenty. Headroom helps avoid clipping — the harsh distortion when an amp runs out of power, which can damage tweeters.
Compare continuous (RMS) power into a stated impedance, across the full frequency range, with both channels driven. “Peak” or “max” figures are marketing numbers and can’t be compared.
Matching an amplifier to speakers
Check impedance
Confirm the amp is rated for your speakers’ nominal impedance (e.g. 4 Ω speakers need an amp stable into 4 Ω).
Check sensitivity
Low-sensitivity speakers (below ~86 dB) benefit from more powerful amps. Very efficient speakers (95 dB+) work well with low-power tube amps.
Check connections
Count your sources: phono, optical, coaxial, USB, HDMI ARC, streaming, headphone output, subwoofer output.
Think about the future
Pre-outs let you add a power amp later; a sub output lets you add bass.
Useful features
- Built-in DAC with optical/coax/USB inputs for TV, computer or CD transport.
- HDMI ARC/eARC to connect the TV and control volume with the TV remote.
- Phono stage (MM, sometimes MC) for turntables.
- Streaming: Wi-Fi platforms, AirPlay, Chromecast, Spotify Connect, Tidal Connect, Roon Ready.
- Tone controls / bass management to adapt to rooms and recordings.
- Room correction (common on AV receivers, increasingly on stereo amps).
Frequently asked questions
Integrated amp or AV receiver?
For stereo music, an integrated amp usually offers better sound quality for the money and simpler use. If you want surround sound for films, an AV receiver is the right tool — and many are good for music too.
Can an amplifier be too powerful for my speakers?
A powerful amp used sensibly is generally safe — the danger comes from playing extremely loud. An underpowered amp pushed into clipping can actually be riskier for tweeters.
Do tubes sound better?
They sound different, and many listeners enjoy their character. Whether it’s “better” is personal. Pair tube amps with efficient speakers for the best results.
Do I need a separate preamp and power amp?
Not for most people. Good integrated amplifiers are excellent. Separates make sense for high-end systems or very demanding speakers.