1. What does an amplifier do?
As the name implies, an amplifier is an electronic device that is able to make an incoming audio signal louder. Since the level signals delivered by CD players, for instance, are very low, the amplifier allows that signal to become audible.
2. Integrated amplifiers
The most common amplifier is an integrated amplifier, combining a pre-amplifier section and a power amplifier section. Think of the pre-amp as the controller, allowing users to choose between incoming signals from different components, and adjusting the output level (or volume) of that signal, while the power amp section allows the amplification of the signal.
3. Pre-amplifiers and Power amplifiers
Instead of a single-box integrated amplifier, there is also the option of separate, dedicated pre-amps and power amps. This is usually a more expensive route to follow, but can offer advantages in terms of quality, power output and upgradeability.
4. Is more power better?
Yes, in most cases it is, even if you don’t need the extra power. Power equals control and headroom: the amplifier has to work less hard to drive the loudspeakers, which means the sound is more authoritative. During small amplifiers hard will lead to the amplifier distorting, which will ultimately damage the loudspeakers.
5. Must the power output of an amplifier be matched to the loudspeaker power rating?
Not necessarily. Overdriving the amplifier is the most common cause of loudspeaker damage. Using loudspeakers with a lower power handling capacity than the amplifier’s output means they can be driven to their full potential, as long as care is taken not to overdrive the speakers.
6. Mono and stereo amplifiers
A monaural amplifiers, or monoblock, is designed to amplify a single channel only. But most hi-fi amplifiers are stereo, which means they amplify two channels – left and right – to create a stereo sound picture.
7. Home theatre or AV amplifiers and receivers
These are multichannel devices that create a surround sound picture by amplifying five, six, seven, or even more channels. The 5.1, 6.1, or 7.1 designation refers to five, six, or seven channels plus one subwoofer channel.
8. Valves versus solid state
Many people think of valve amplifiers as old-fashioned, but there are many contemporary valve amps. However, before the advent of the transistor, all amplifiers used vacuum tube designs. today, they are deemed inefficient, but their characteristically mellow sound can be pleasing. Solid-state amplifiers use transistors, and are typically more reliable, more efficient and achieve higher outputs.
9. Amplifier classes
There are many different amplifier classes, but in hi-fi terms, Class A and AB are the most common analogue configurations, while Class D is a more recent digital, switching design. Regardless of class, it is what the amplifier sounds like that matters most.
10. What is a phono stage?
A phono stage is specialised step-up amplifier designed to boost the very low output signal from a turntable’s phono cartridge to levels that a normal amplifier or pre-amplifier can cope with. Some integrated amps and pre-amps have built-in phono stages.