A pre-amplifier sits between your audio sources and the power amplifier in a hi-fi system. Its main job is to receive, select and manage audio signals before they are sent to the power amplifier.

When you connect sources such as a CD player, turntable, music streamer or DAC, the pre-amplifier allows you to select which source you want to hear. It also provides volume control, adjusting the signal level before it reaches the power amplifier.

A pre-amplifier may also perform additional functions. Depending on the design, it can include a phono stage for turntables, digital inputs and a built-in DAC, tone controls, balance adjustment, headphone output or home-cinema connectivity.

The power amplifier then takes the controlled signal from the pre-amplifier and increases its power enough to drive the loudspeakers. In a traditional separates system, the pre-amplifier therefore acts as the control centre while the power amplifier provides the muscle.
Some modern integrated amplifiers combine the pre-amplifier and power amplifier in a single chassis. Other products, such as active loudspeakers and some all-in-one streaming systems, incorporate these functions internally.

A good pre-amplifier should provide clean signal handling, low noise, appropriate connectivity and accurate volume control. Choosing the right model also requires checking that its inputs and outputs are compatible with the other components in the system.