None of today's audio systems would be possible without the help of modern audio amplifiers which strive to satisfy higher and higher demands regarding power and audio fidelity. There is a large amount of amplifier designs and models. All of these differ in terms of performance. I will explain some of the most common amplifier terms such as "class-A", "class-D" and "t amps" to help you figure out which of these amps is best for your application. Also, after reading this article you should be able to understand the amplifier specs which manufacturers publish.
The basic operating principle of an audio amp is fairly straightforward. An audio amp will take a low-level audio signal. This signal usually comes from a source with a fairly high impedance. It then converts this signal into a large-level signal. This large-level signal can also drive speakers with low impedance. The type of element used to amplify the signal depends on which amplifier architecture is used. Some amps even use several types of elements. Typically the following parts are used: tubes, bipolar transistors and FETs.
Tube amplifiers used to be common a few decades ago. A tube is able to control the current flow according to a control voltage which is connected to the tube. Unfortunately, tube amplifiers have a fairly high amount of distortion. Technically speaking, tube amplifiers will introduce higher harmonics into the signal. However, this characteristic of tube amps still makes these popular. Many people describe tube amps as having a warm sound versus the cold sound of solid state amps.
Also, tube amps have fairly low power efficiency and thus radiate a lot of power as heat. Yet another drawback is the high price tag of tubes. This has put tube amps out of the ballpark for many consumer devices. As a result, the majority of audio products nowadays uses solid state amps. I will explain solid state amps in the following paragraphs.
The first generation models of solid state amps are known as "Class-A" amps. Solid-state amps use a semiconductor rather than a tube to amplify the signal. Usually bipolar transistors or FETs are being used. In a class-A amp, the signal is being amplified by a transistor which is controlled by the low-level audio signal. In terms of harmonic distortion, class-A amps rank highest amongst all types of audio amps. These amps also usually exhibit very low noise. As such class-A amps are ideal for very demanding applications in which low distortion and low noise a crucial. Class-A amps, however, waste most of the energy as heat. Therefore they usually have large heat sinks and are fairly heavy.
By using a series of transistors, class-AB amps improve on the low power efficiency of class-A amps. The operating working area is divided in two separate areas. These two areas are handled by separate transistors. Each of these transistors works more efficiently than the single transistor in a class-A amp. The higher efficiency of class-AB amps also has two other advantages. Firstly, the required amount of heat sinking is reduced. Therefore class-AB amps can be made lighter and smaller. For that reason, class-AB amps can be made cheaper than class-A amps. Class-AB amps have a drawback though. Every time the amplified signals transitions from one region to the other, there will be some distortion generated. In other words the transition between these two areas is non-linear in nature. Therefore class-AB amps lack audio fidelity compared with class-A amps.
Class-D amps are able to achieve power efficiencies above 90% by using a switching transistor which is constantly being switched on and off and thus the transistor itself does not dissipate any heat. The switching transistor, which is being controlled by a pulse-width modulator generates a high-frequency switching component which has to be removed from the amplified signal by using a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amps having larger audio distortion than other types of amplifiers.
More recent audio amps incorporate some sort of mechanism to minimize distortion. One approach is to feed back the amplified audio signal to the input of the amp to compare with the amplified signal. The difference signal is then used to correct the switching stage and compensate for the nonlinearity. "Class-T" amps (also called "t-amp") use this type of feedback mechanism and therefore can be made extremely small while achieving low audio distortion.
The basic operating principle of an audio amp is fairly straightforward. An audio amp will take a low-level audio signal. This signal usually comes from a source with a fairly high impedance. It then converts this signal into a large-level signal. This large-level signal can also drive speakers with low impedance. The type of element used to amplify the signal depends on which amplifier architecture is used. Some amps even use several types of elements. Typically the following parts are used: tubes, bipolar transistors and FETs.
Tube amplifiers used to be common a few decades ago. A tube is able to control the current flow according to a control voltage which is connected to the tube. Unfortunately, tube amplifiers have a fairly high amount of distortion. Technically speaking, tube amplifiers will introduce higher harmonics into the signal. However, this characteristic of tube amps still makes these popular. Many people describe tube amps as having a warm sound versus the cold sound of solid state amps.
Also, tube amps have fairly low power efficiency and thus radiate a lot of power as heat. Yet another drawback is the high price tag of tubes. This has put tube amps out of the ballpark for many consumer devices. As a result, the majority of audio products nowadays uses solid state amps. I will explain solid state amps in the following paragraphs.
The first generation models of solid state amps are known as "Class-A" amps. Solid-state amps use a semiconductor rather than a tube to amplify the signal. Usually bipolar transistors or FETs are being used. In a class-A amp, the signal is being amplified by a transistor which is controlled by the low-level audio signal. In terms of harmonic distortion, class-A amps rank highest amongst all types of audio amps. These amps also usually exhibit very low noise. As such class-A amps are ideal for very demanding applications in which low distortion and low noise a crucial. Class-A amps, however, waste most of the energy as heat. Therefore they usually have large heat sinks and are fairly heavy.
By using a series of transistors, class-AB amps improve on the low power efficiency of class-A amps. The operating working area is divided in two separate areas. These two areas are handled by separate transistors. Each of these transistors works more efficiently than the single transistor in a class-A amp. The higher efficiency of class-AB amps also has two other advantages. Firstly, the required amount of heat sinking is reduced. Therefore class-AB amps can be made lighter and smaller. For that reason, class-AB amps can be made cheaper than class-A amps. Class-AB amps have a drawback though. Every time the amplified signals transitions from one region to the other, there will be some distortion generated. In other words the transition between these two areas is non-linear in nature. Therefore class-AB amps lack audio fidelity compared with class-A amps.
Class-D amps are able to achieve power efficiencies above 90% by using a switching transistor which is constantly being switched on and off and thus the transistor itself does not dissipate any heat. The switching transistor, which is being controlled by a pulse-width modulator generates a high-frequency switching component which has to be removed from the amplified signal by using a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amps having larger audio distortion than other types of amplifiers.
More recent audio amps incorporate some sort of mechanism to minimize distortion. One approach is to feed back the amplified audio signal to the input of the amp to compare with the amplified signal. The difference signal is then used to correct the switching stage and compensate for the nonlinearity. "Class-T" amps (also called "t-amp") use this type of feedback mechanism and therefore can be made extremely small while achieving low audio distortion.
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You can get further information concerning class-t amps and stereo amplifiers from Amphony's website.
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