In the previous section, we talked about pre-amplifiers so you might ask, what is an amplifier?

An amplifier is what takes the low-level audio signals form your sources and amplifies them electrically to drive your speakers. As you can imagine, this is an integral part of your home theater setup.

Most people call it an amp, and most recommend one that does at least 50 watts per channel.

We’ll take a look at some technical details of what an amplifier is, why amplification is important in modern electronic equipment, why an amplifier is one of the most commonly used electronic devices in the world, and how amplifiers are described according to the properties of their inputs and outputs.

Let’s dive in.

What is an amplifier?

An amplifier is a device that boosts the power of analog audio signals that are coming out of the controller to drive the speakers and create sound. Basically, this is usually a big box, with an on and off switch, speaker terminals, and one or more RCA jack audio inputs on the back for connecting your AV controller.

As we mentioned in our introduction to separates article, you do not control volume with the power amplifier, the AV controller does that.

Amplifiers, no matter if they are separate or in a receiver, use transistors to make their power. In the good old days, manufacturers used vacuum tubes to power their amplifiers, and some really expensive ones still do use them. And that is because some audio enthusiasts prefer the sound of the tubes.

However, most inexpensive receivers these days make use of an integrated circuit, which provide power generating transistors for several audio channels on a single chip. Better quality receivers have discrete amplifier output transistors, that is to say separate transistors for each channel. This discrete design typically allows for more power and better sound.

Amp ratings

Amplifiers are classified and given ratings by several different parameters. These include gain, bandwidth, efficiency, linearity, noise, output dynamic range, slew rate, and stability among others. These are the properties that you will have to keep in mind when buying a dedicated amp or an AV receiver that comes integrated with one.

All amplifiers have gain, which is simply the ratio between the magnitude of output and input signals. And most amps are designed to be linear, which is to say they provide constant gain for any normal input and output level. If the gain of the amplifier is not linear, its output signal can become distorted.

Go beyond home theaters, and you will find that amplifiers have widespread uses.

They are the basic building blocks of a vast number of circuits, and come in various forms, shapes and sizes. Because after all, they are simply electronic devices that increases the power of a signal, hence their name.

In the world of home theaters, however, the purpose of an amp is to receive a small electrical signal and enlarge or amplify it. Enough, to power a loudspeaker. In your AV receiver, for example, an amplifier will receive an input signal from a source like a Bluray player, and then create an enlarged replica of the original smaller signal. So, the more powerful an amp you have, the more powerful a signal it can send to drive your speaker system.

As you can imagine, there are variety of different types of power amps available, each with its own ratings and specifications.

Luckily, it’s not hard to find out and define the amplification power you need on your home theater equipment, with most manufactures clearly listing these specifications. It all comes down to mixing and matching with the room size of your home theater, and how loud you like your entertainment.