Amplifier: what it is, how it works, and how to choose

The sound of musical instruments or recordings broadcast through a laptop is not loud enough for a party or the performance of songs in a cafe. The power of the speakers of the music system is not enough. In order to play louder and sound clearer, use special equipment - amplifiers.

How an amplifier works

It does not literally amplify the sound, but such equipment works in a very interesting way. Its action resembles what happens when we open the water faucet. The water flow can be made stronger, weaker or stopped altogether. It is also possible to change the sound. From the power supply, a powerful current flows through the speaker connected to the amplifier. The inlet and outlet transistors act as the «tap». They regulate the flow of sound.

The input signal accurately replicates the output signal. To achieve this, in class-AB audio amplifiers, the transistors keep the sound flow ajar, not open it completely. Then there is no mismatch of input and output flow. As a result, there is a constant loss of energy, as if a trickle of water were constantly flowing from the faucet. The efficiency of a Class AB sound amplifier is low.

Class D audio amplifiers are set up the same way, only the current flow is controlled by a signal which is different from the input. From the head unit the signal goes continuously, but its amplitude changes. It becomes pulsed at the input and when the amplitude is constant the signal is periodically interrupted. In between, the duration of pulses and pauses change. This signal goes to the transistors. They either fully open or fully close without averaging. In this way, energy is used as efficiently as possible, and the efficiency of a Class D audio amplifier is close to 100%.

Before the signal is applied to the loudspeaker system, it reverts to its normal form. The output produces an amplified signal that goes to the speakers.

There are amplifiers both stationary and mobile and car amplifiers. They differ from stationary amplifiers in power, voltage and size.

How to choose an amplifier

Before buying an amplifier, you need to know the parameters of your acoustic installation. It is matched with a suitable model in terms of performance.

If your loudspeaker system is not very powerful, it is not worth buying an amplifier which is too powerful. It will operate at the limits of your audio source. You will be overpaying for power which cannot be used. An acceptable rating for an amplifier is one which exceeds the power of the loudspeakers by 10-15kW.

The impedance of both devices must match. Often it is 4 ohms. If the loudspeaker's impedance is different, the amplifier's should be matched.

Amplifiers are equipped with additional options:

• A built-in sound processor helps you tune the sound easier and faster.
• The bass adjuster in the sound amplifier will help to tweak the bass so that you can fully feel the bass.
• High-level input - most amplifiers have this option.

If you want a compact amplifier, it should have a class D, indicating that it is a modern system, but also the most expensive. But, the sound will be of high quality. If you want it cheaper, then you can choose a good model from the class AB lineup. It will be more oversized.