That an amplifier is an important part of your audio system is probably nothing new. There are many different types of amplifier. Each type has its own properties and is intended for a specific type of device. Different classes can also be distinguished. In this article we first briefly discuss what an amplifier is again and then answer the question ‘what class amplifier is the best?’
WHAT IS AN AMPLIFIER AGAIN?
As the name suggests, an amplifier amplifies the signal from a source. It is usually not strong enough to be played through your speakers. The amplifier can be a classic HiFi-part. But also, for example, a much more complicated AV-receiver. You will find amplifiers everywhere, big and small. Chances are that there is currently an amplifier in your pocket or that you even hold it in your hand.
Many devices have a built-in amplifier, such as the speakers of your computer. This can be recognized by the fact that there is a volume button on the speaker. However, if you have high-quality speakers, you naturally want them to play all of your audio: your record player, game console, television and so on. Besides that not all of these devices are suitable for direct playback, it is inconvenient to always disconnect and exchange a device. An pre-amplifier or integrated amplifier solves these problems.
ARE THERE ANY DIFFERENCES BETWEEN AMPLIFIERS?
Amplifiers have one function: to amplify an audio signal. Nevertheless, they are available in different sizes and with different qualities. This is necessary, because amplifiers are used in all kinds of different devices. For example, the signal in a quality speaker is very different than the signal in some headphones. And a mobile phone must be able to play sound through the built-in speakers as well as the headphones. There are different types of amplifiers for all these different requirements. To get a good idea of the differences we discuss the main types.
Most speaker systems contain a power amplifier in combination with a pre amplifier. The power amp is at the end of the chain, just in front of the speakers. However, these amplifiers cannot simply be used: the volume controle is missing. Therefore, it is combined with a seperate pre amp. This contains everything a power amp lacks: analog inputs, volume control, any additional processing and perhaps digital inputs and streaming. Different classes can be distinguished within the power amps.
Often, an integrated amplifier is chosen. These have the functions of both a pre- and a power amplifier. An advantage of this amplifier is that all kinds of input devices, like a CD player, TV and other devices with sound output (DAC, streaming and other functions) can be added.
Are you more of the old familiar vinyl then chances are that you use a phono amplifier at home. It has only one purpose: to amplify the weak signal from a turntable so that it can be played. Many preamps and integrated amplifiers also have a phono input, so it is not necessary for everyone. As mentioned earlier, headphones have different requirements than speakers. Special headphone amplifier have therefore been made for these products.
WHY DIFFERENT CLASSES OF AMPLIFIERS?
If you have ever put together a system yourself, you will undoubtedly know that amplifiers are available in different classes. Class A, B, AB, and so on. These simply indicate what technique is used to get a weak signal amplified so that it can come out of the speakers. A common source such as a Blu-ray player or turntable delivers too weak signal to play directly on the speakers. Sound is nothing more than vibration, and your speakers need power to vibrate. The louder the music, the more air has to be set in motion, the more power is needed.
In the HiFi world there is a lot of talk about class A and class D amplifiers. This is less evident in home cinema. Here you mainly see class AB or class D amplifiers. We will discuss the most important classes for the Hifi world.
A CLASS – THE PURE ONE
In general, A class amplifiers provide the best results. Without diving too much into technical details, for this we would like to refer you to this, we can say that an A class amplifier delivers perfect linear processing. This means that the input signal is perfectly amplified at all points to a higher power.
Why doesn’t everyone choose this class? That’s because they have a major drawback. This perfect amplification is only possible by continuously energizing the part, even if there is nothing or almost nothing to amplify in terms of sound. An A class amplifier that has been forgotten to turn off consumes just as much power as one under heavy load. In addition, these amplifiers are hugely inefficient. About 70 to 90 percent of the consumed electricity is converted into heat. If you like to listen to music at a 100 watts of power per channel, then you use about 1000 watts of electricity per channel. When you use stereo this will be doubled, since you use two channels.
B CLASS – THE ECONOMICAL
The major problem of A class amplifiers has been attempted to solve with B class amplifiers. The output stage uses a small quiescent which keeps the amplifier a lot cooler. With this type of amplifiers, the audio signal is divided into a negative and positive half-wave. These half waves each go to their own transistor and are amplified there. Because the positive half wave and the second half wave are generated in two different electronic parts these have to be brought together to form the original full sine wave. The crossing point at 0 Volt causes problems because of the difficulty to match these two waves: the signal will be distorted. This is what we call cross-over distortion. Such an amplifier is unthinkable for the high-end segment. In practice, these are mainly used when only speech needs to be amplified, for example with an megaphone.
AB CLASS – THE FLEXIBLE
Class AB has been developed as an interim solution. With these amplifiers, the output stage is switched to class A at relatively low power. When more power is requested, it switches to class B. In this way the temperature remains pleasant and the yield increases. Where A class amplifiers age quicly due to extreme heat, this remains within limits at the AB class. Practically, you will find that at a normal listening level you listen in class A most of the time. The class B is for headroom.
D CLASS – THE DIGITAL?
A logical next step would be class C. Class C, E and F are used in the radio transmission technique. The next letter in the alphabet is therefore the “D”. Amplifiers that work according to the so-called switching principle are referred to as class D. Also known as switch-mode or PWM (Pulse-Width Modulation). Due to the existence of digital amplifiers, it is often thought that the “D” stands for digital. However, a class D amplifier is nothing more than a switching analog amplifier. This switching is done via a control that works on the basis of the incoming signal. This control can be digital, which can be very confusing.
D class amplifiers are increasingly used in high end audio. Due to the super fast switching, these amplifiers are extremely feasible. Where an A class amplifier has only 10 to 30 percent efficiency, with D class this increases to 90 or even 95 percent. This means that these amplifiers do not get warm and the size can remain small. Exactly what is needed with an AV receiver and TV audio devices such as sound bars. Also in terms of performance, D class amplifiers have undergone enormous development. Where A class amplifiers traditionally delivered the best performance, there is hardly any difference nowadays.
A disadvantage can be that it is difficult to get D class amplifiers right. The power supply must be of high quality and filters must be fitted after the reinforcement hatch to remove high-frequency interference caused by control. However, this does not mean that it is not possible to experience absolute top quality audio with a class D amplifier. This solution can increase the price, so that it is not reserved for the lower segment speakers.
GOOD POWER SUPPLY
Many people choose a D class amplifier because of the efficiency and to reduce costs. It is important to know that there are different qualities of class D amplifiers. The power supply plays an important role in this. A good amplifier stands or falls with the power supply. It must be powerful enough but also stable. Of course you want an explosion in a film to appear realistic.
The Origin speaker is equipped with an extremely efficient and powerful class D amplifier with all the latest technology. Wondering how this sounds? Come along for a listening session and we will be happy to tell you all about it.