Power amplifiers are at the very core of each home theater system. As the quality and output power demands of modern loudspeakers increase, so do the requirements of stereo amps. With the ever growing amount of models and design topologies, like "tube amplifiers", "class-A", "class-D" along with "t amplifier" types, it is becoming more and more demanding to pick the amp that is perfect for a particular application. This article is going to explain a few of the most popular terms and clarify a few of the technical jargon which amp producers regularly utilize.
The main operating principle of an audio amplifier is quite simple. An audio amplifier will take a low-level music signal. This signal typically originates from a source with a rather high impedance. It subsequently converts this signal into a large-level signal. This large-level signal may also drive speakers with small impedance. Depending on the type of amplifier, one of several kinds of elements are used in order to amplify the signal including tubes and transistors.
Tube amplifiers used to be widespread several decades ago. A tube is able to control the current flow in accordance to a control voltage which is connected to the tube. One problem with tubes is that they are not extremely linear when amplifying signals. Aside from the original audio, there are going to be overtones or higher harmonics present in the amplified signal. Thus tube amplifiers have fairly large distortion. Today, tube amplifiers still have many followers. The primary reason is that the distortion which tubes bring about are frequently perceived as "warm" or "pleasant". Solid state amplifiers with small distortion, on the other hand, are perceived as "cold". A different downside of tube amps, however, is the small power efficiency. The bulk of power that tube amplifiers consume is being dissipated as heat and merely a portion is being transformed into audio power. Yet another drawback is the big price tag of tubes. This has put tube amps out of the ballpark for a lot of consumer devices. Consequently, the majority of audio products nowadays employs solid state amps. I am going to describe solid state amplifiers in the following sections.
One more drawback of tube amplifiers, however, is the low power efficiency. The bulk of power that tube amps use up is being dissipated as heat and merely a portion is being converted into audio power. Yet one more disadvantage is the high price tag of tubes. This has put tube amplifiers out of the ballpark for a lot of consumer devices. Because of this, the majority of audio products these days uses solid state amplifiers. I am going to describe solid state amps in the subsequent paragraphs.
By using a number of transistors, class-AB amps improve on the low power efficiency of class-A amps. The operating area is divided into two distinct areas. These 2 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 2 other benefits. Firstly, the required number of heat sinking is minimized. For that reason class-AB amps can be made lighter and smaller. For that reason, class-AB amps can be manufactured cheaper than class-A amps. When the signal transitions between the two separate areas, however, a certain amount of distortion is being created, thereby class-AB amps will not achieve the same audio fidelity as class-A amps.
To improve on the small efficiency of class-A amps, class-AB amps employ a series of transistors which each amplify a separate area, each of which being more efficient than class-A amplifiers. As such, class-AB amps are typically smaller than class-A amplifiers. Nonetheless, this topology adds some non-linearity or distortion in the region where the signal switches between those areas. As such class-AB amplifiers generally have larger distortion than class-A amps.
Class-D amplifiers are able to attain power efficiencies higher than 90% by employing a switching transistor that is continually being switched on and off and thereby 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 needs to be removed from the amplified signal by using a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities that result in class-D amplifiers having larger music distortion than other kinds of amps. To resolve the problem of large audio distortion, new switching amplifier designs include feedback. The amplified signal is compared with the original low-level signal and errors are corrected. One kind of audio amplifiers that makes use of this kind of feedback is known as "class-T" or "t amplifier". Class-T amplifiers feed back the high-level switching signal to the audio signal processor for comparison. These amplifiers have small audio distortion and can be manufactured extremely small.
The main operating principle of an audio amplifier is quite simple. An audio amplifier will take a low-level music signal. This signal typically originates from a source with a rather high impedance. It subsequently converts this signal into a large-level signal. This large-level signal may also drive speakers with small impedance. Depending on the type of amplifier, one of several kinds of elements are used in order to amplify the signal including tubes and transistors.
Tube amplifiers used to be widespread several decades ago. A tube is able to control the current flow in accordance to a control voltage which is connected to the tube. One problem with tubes is that they are not extremely linear when amplifying signals. Aside from the original audio, there are going to be overtones or higher harmonics present in the amplified signal. Thus tube amplifiers have fairly large distortion. Today, tube amplifiers still have many followers. The primary reason is that the distortion which tubes bring about are frequently perceived as "warm" or "pleasant". Solid state amplifiers with small distortion, on the other hand, are perceived as "cold". A different downside of tube amps, however, is the small power efficiency. The bulk of power that tube amplifiers consume is being dissipated as heat and merely a portion is being transformed into audio power. Yet another drawback is the big price tag of tubes. This has put tube amps out of the ballpark for a lot of consumer devices. Consequently, the majority of audio products nowadays employs solid state amps. I am going to describe solid state amplifiers in the following sections.
One more drawback of tube amplifiers, however, is the low power efficiency. The bulk of power that tube amps use up is being dissipated as heat and merely a portion is being converted into audio power. Yet one more disadvantage is the high price tag of tubes. This has put tube amplifiers out of the ballpark for a lot of consumer devices. Because of this, the majority of audio products these days uses solid state amplifiers. I am going to describe solid state amps in the subsequent paragraphs.
By using a number of transistors, class-AB amps improve on the low power efficiency of class-A amps. The operating area is divided into two distinct areas. These 2 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 2 other benefits. Firstly, the required number of heat sinking is minimized. For that reason class-AB amps can be made lighter and smaller. For that reason, class-AB amps can be manufactured cheaper than class-A amps. When the signal transitions between the two separate areas, however, a certain amount of distortion is being created, thereby class-AB amps will not achieve the same audio fidelity as class-A amps.
To improve on the small efficiency of class-A amps, class-AB amps employ a series of transistors which each amplify a separate area, each of which being more efficient than class-A amplifiers. As such, class-AB amps are typically smaller than class-A amplifiers. Nonetheless, this topology adds some non-linearity or distortion in the region where the signal switches between those areas. As such class-AB amplifiers generally have larger distortion than class-A amps.
Class-D amplifiers are able to attain power efficiencies higher than 90% by employing a switching transistor that is continually being switched on and off and thereby 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 needs to be removed from the amplified signal by using a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities that result in class-D amplifiers having larger music distortion than other kinds of amps. To resolve the problem of large audio distortion, new switching amplifier designs include feedback. The amplified signal is compared with the original low-level signal and errors are corrected. One kind of audio amplifiers that makes use of this kind of feedback is known as "class-T" or "t amplifier". Class-T amplifiers feed back the high-level switching signal to the audio signal processor for comparison. These amplifiers have small audio distortion and can be manufactured extremely small.
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