What is a Preamp, and do I really need one?

Every audio system Requires amplification. In a traditional hi-fi setup, the speakers are always “passive” – that is, they do not produce their own power. Instead, they must receive an amplified audio signal from an external source, aptly called an amplifier, in order to do their job. Even in a more modern, self-contained audio system (like the Sonos Era 100, for example), the drivers that produce the sound must be amplified for it to work—all of this happens in a single box rather than via separate hi-fi hardware.

But if you’ve heard of speakers, you’ve probably also heard of preamps (often referred to as “preamps”) and wondered where they fit into a sound system, and whether you need them. Let’s answer these questions, shall we?

What does Preamp do?

An audio signal needs a lot of attention before it’s ready for amplification, so the question ultimately arises, “What does an amplifier do?” Widely contains its own answer. The amplifier takes care of everything that needs to be done before the audio signal (sent from the music source) is amplified and sent to the system’s speakers.

In a stand-alone audio system like the Sonos speaker, the preamp and tweeter are in the same enclosure, along with the speaker drivers that actually deliver the sound. Even in more sophisticated discrete hi-fi setups, the preamp part of the proceedings is still handled out of sight, inside the amplifier. These types of amplifiers are known as “integrated speakers” and contain both the function of a preamp and a subwoofer.

However, some people prefer to separate this function, as you may find a preamp as its own piece of equipment, coupled with a power amplifier. In these cases, the amplifier allows you to select the source of the music you want to hear (most have a selection of input options to support a system with multiple sources), as well as set and adjust the volume.

The amplifier also ensures that the audio signal is at ‘line level’ – that is, the standard voltage strength of the audio signal transmitted between components – and sends it to be amplified, ready to finally go to the speakers.

Does an external speaker improve sound quality?

Hi-fi doctrine says that the individual functions in a system should be kept as separate as possible if we are to achieve the best results. The thinking goes that by keeping the electrical activity as protected and self-contained as possible, the audio signal has the best chance of remaining as pure and uncolored as possible.

By dividing the preamplifier and amplifier functions into separate boxes, there should be less electrical noise and interference around the signal compared to putting them all in one box.