The amplifier's function is to amplify audio signals from CD players and other sources, so that they become powerful enough to power your speakers. It doesn't sound like anything spectacular, but it is in fact a rather complex and a demanding affair.
To reproduce a music signal at a high level, with little or no audible distortion through heavy powered speakers, is a tricky combination of power and finesse. It requires both a solid power supply and high-quality components, not to mention a structure where nothing is left to chance. Therefore, the best amplifiers tend to cost a considerable amount of money.
Amplifier power is measured in watts, and the more watts, the higher the volume. Quality, however, can not be measured in watts, and for its part sound quality is more important to have rather than pumping out hundreds of watts that sound awful. The most important characteristic of an amplifier is that it must be fast and stable, with enough power reserves to tackle the challenges it receives, both from the music source and the speakers it powers.
When choosing the amplifier, it is often tempting to choose the most powerful one. In some cases, this is not a stupid thought, but remember that the amplifier will work best with your particular speakers. Power alone is not enough to drive speakers with quality sound, but it makes it easier to control them.
An integrated amplifier is the "admission" to a good hi-fi system. This is a complete amplifier where the input selector, volume control, power supply and power stage are housed in the same box. You can easily connect to all audio sources for input and speakers output. In a compact and affordable integrated amplifier there is no room for a large power supply, so you only get a relatively low 2 x 30 and 2 x 80 watts.
Benefits: An affordable integrated amplifier provides all the features you need in a single device at a reasonable price.
Disadvantages: A small integrated amplifier has limited power output and therefore will lack the ability to power speakers to their maximum ability. Therefore, it pays to be smart by matching speakers - select either a few sensitive floorstanding speakers or small bookshelf speakers.
Larger Integrated Amplifiers
The larger and more lavish integrated amplifiers have a stronger and more stable power supply that provides higher output power, typically between 80 and 150 watts per channel. It is sufficient to power most hi-fi speakers with high precision even at high sound levels. Most amplifiers use regular analog inputs, but some modern varieties also come with a built-in D/A converter, where you can connect to digital audio sources and improve sound quality. Some amplifiers can also be connected to a network and can stream music from your hard drive.
Benefits: A larger integrated amplifier has enough power and finesse to drive most hi-fi speakers with high precision even at high sound levels.
Disadvantages: Larger space requirements and higher weight means you have to be a little more thoughtful with the position of the amplifier.
As we move up the quality ladder it becomes more common to see separate amplifiers. Here the control section and power section is separated from each other in a separate enclosure, in which a preamplifier controls inputs and volume control, while the latter takes care of the amplification of the signal. There is room for a proper power supply and the result can be 100-250 watts or more, which is well suited to operate demanding speakers.
Benefits: Separate amplifier units has several advantages, such as each device gets its own dedicated power supply, so that they can work independently. In addition, it is an advantage to separate the powerful power supply in a power amplifier from the more sensitive control section. This becomes all the more beneficial to large and powerful power amplifiers, or in cases where you use multiple amplifier channels (bi-amping).
Disadvantages: Separate amplifiers tend to weigh more, they take more space on the shelf and require an additional set of cables. You also pay a higher price for the additional unit.
Mono Amplifiers are in many ways the optimal amplifier. You have a separate amplifier for each channel that is completely separated from each other. Eliminating crosstalk and other interference between channels. Mono amplifiers also have the advantage that they can be placed closer to the speakers and use shorter speaker cables, which can be beneficial for sound quality. With such a configuration, it is an advantage to use balanced cables (XLR) from the preamplifier to avoid noise you can get on long cable runs.
Selecting the Correct Amplifier
Now that you understand the difference between different amplifier types the time has come to choose the right amplifier for your particular system.
The amplifier should match the quality of the rest of your electronics, but it is especially important that it matches your speakers. A small budget amplifier will quickly become irritating if you intend to operate large and demanding high-end speakers, because it has neither the precision or muscles to power them the way they are intended.
The opposite, however, can work well: A lavish and powerful amplifier can make even cheap speakers sound surprisingly good, because the high quality helps to mask the speakers weaknesses. But, instead of spending £500 on the speakers and £2000 on the amplifier, you will get a better end result if you spend roughly an equal amount on each component.
Listen before You Buy
Ensure that the amplifier can power your speakers before buying. The safest way to do this is to visit a store and get a demonstrated on a setup that is similar to yours.
Choose a good amp that you can afford, and make sure it is as powerful and stable as you need it. A horn speaker with high sensitivity can play fantastic on a 20 watt amplifier because it is undemanding when it comes to electrical load. An electrostatic speaker is far more demanding, because it is far less efficient and has low-impedance. Low impedance and low sensitivity can drain even the toughest amplifier in a flash, leaving the user with a piping hot amplifier and soaring distortion.