Music amplifiers are at the very center of every home theater product. As the quality and output power demands of modern loudspeakers increase, so do the requirements of audio amplifiers. There is a big quantity of amplifier concepts and types. All of these differ regarding performance. I am going to describe some of the most popular amp terms like "class-A", "class-D" and "t amps" to help you figure out which of these amplifiers is ideal for your application. In addition, after understanding this article you should be able to understand the amplifier specifications that makers issue. Simply put, the purpose of an audio amp is to convert a low-power audio signal into a high-power music signal. The high-power signal is big enough to drive a loudspeaker adequately loud. Depending on the kind of amplifier, one of several types of elements are used to amplify the signal such as tubes as well as transistors.
A couple of decades ago, the most common kind of audio amplifier were tube amps. Tube amps use a tube as the amplifying element. The current flow through the tube is controlled by a low-level control signal. In that way the low-level audio is converted into a high-level signal. One problem with tubes is that they are not extremely linear when amplifying signals. Aside from the original audio, there will be overtones or higher harmonics present in the amplified signal. For that reason tube amps have quite large distortion. Though, this characteristic of tube amplifiers still makes these popular. Many people describe tube amps as having a warm sound as opposed to the cold sound of solid state amplifiers.
A number of decades ago, the most popular type of audio amplifier were tube amps. Tube amps use a tube as the amplifying element. The current flow through the tube is controlled by a low-level control signal. In that way the low-level audio is transformed into a high-level signal. One dilemma with tubes is that they are not very linear while amplifying signals. Aside from the original audio, there will be overtones or higher harmonics present in the amplified signal. Consequently tube amps have rather large distortion. Today, tube amplifiers still have many followers. The primary reason is that the distortion which tubes cause are frequently perceived as "warm" or "pleasant". Solid state amps with small distortion, on the other hand, are perceived as "cold".
Solid state amplifiers replace the tube with semiconductor elements, typically bipolar transistors or FETs. The earliest kind of solid-state amps is often known as class-A amplifiers. In a class-A amp, the signal is being amplified by a transistor which is controlled by the low-level audio signal. If you require an ultra-low distortion amp then you might wish to investigate class-A amps because they offer amongst the lowest distortion of any audio amplifiers. The major disadvantage is that much like tube amps class A amplifiers have quite small efficiency. As a result these amplifiers require large heat sinks in order to radiate the wasted energy and are typically quite heavy.
To improve on the small efficiency of class-A amplifiers, class-AB amplifiers employ a series of transistors that each amplify a separate area, each of which being more efficient than class-A amplifiers. The higher efficiency of class-AB amps also has two further advantages. Firstly, the required number of heat sinking is reduced. For that reason class-AB amps can be manufactured lighter and smaller. For that reason, class-AB amps can be manufactured cheaper than class-A amplifiers. Though, this topology adds some non-linearity or distortion in the area where the signal switches between those areas. As such class-AB amps generally have larger distortion than class-A amplifiers.
To further improve the audio efficiency, "class-D" amps utilize a switching stage which is continually switched between two states: on or off. None of these two states dissipates power inside the transistor. Therefore, class-D amplifiers regularly are able to attain power efficiencies beyond 90%. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). Typical switching frequencies are in the range of 300 kHz and 1 MHz. This high-frequency switching signal has to be removed from the amplified signal by a lowpass filter. Usually a simple first-order lowpass is being utilized. Due to non-linearities of the pulse-width modulator and the switching transistor itself, class-D amps by nature have amongst the highest audio distortion of any audio amplifier.
More recent audio amplifiers incorporate some type of means in order to reduce distortion. One method is to feed back the amplified audio signal to the input of the amp to compare with the original signal. The difference signal is subsequently utilized in order to correct the switching stage and compensate for the nonlinearity. "Class-T" amps (also known as "t-amp") make use of this sort of feedback mechanism and therefore can be manufactured very small whilst attaining small music distortion.
A couple of decades ago, the most common kind of audio amplifier were tube amps. Tube amps use a tube as the amplifying element. The current flow through the tube is controlled by a low-level control signal. In that way the low-level audio is converted into a high-level signal. One problem with tubes is that they are not extremely linear when amplifying signals. Aside from the original audio, there will be overtones or higher harmonics present in the amplified signal. For that reason tube amps have quite large distortion. Though, this characteristic of tube amplifiers still makes these popular. Many people describe tube amps as having a warm sound as opposed to the cold sound of solid state amplifiers.
A number of decades ago, the most popular type of audio amplifier were tube amps. Tube amps use a tube as the amplifying element. The current flow through the tube is controlled by a low-level control signal. In that way the low-level audio is transformed into a high-level signal. One dilemma with tubes is that they are not very linear while amplifying signals. Aside from the original audio, there will be overtones or higher harmonics present in the amplified signal. Consequently tube amps have rather large distortion. Today, tube amplifiers still have many followers. The primary reason is that the distortion which tubes cause are frequently perceived as "warm" or "pleasant". Solid state amps with small distortion, on the other hand, are perceived as "cold".
Solid state amplifiers replace the tube with semiconductor elements, typically bipolar transistors or FETs. The earliest kind of solid-state amps is often known as class-A amplifiers. In a class-A amp, the signal is being amplified by a transistor which is controlled by the low-level audio signal. If you require an ultra-low distortion amp then you might wish to investigate class-A amps because they offer amongst the lowest distortion of any audio amplifiers. The major disadvantage is that much like tube amps class A amplifiers have quite small efficiency. As a result these amplifiers require large heat sinks in order to radiate the wasted energy and are typically quite heavy.
To improve on the small efficiency of class-A amplifiers, class-AB amplifiers employ a series of transistors that each amplify a separate area, each of which being more efficient than class-A amplifiers. The higher efficiency of class-AB amps also has two further advantages. Firstly, the required number of heat sinking is reduced. For that reason class-AB amps can be manufactured lighter and smaller. For that reason, class-AB amps can be manufactured cheaper than class-A amplifiers. Though, this topology adds some non-linearity or distortion in the area where the signal switches between those areas. As such class-AB amps generally have larger distortion than class-A amplifiers.
To further improve the audio efficiency, "class-D" amps utilize a switching stage which is continually switched between two states: on or off. None of these two states dissipates power inside the transistor. Therefore, class-D amplifiers regularly are able to attain power efficiencies beyond 90%. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). Typical switching frequencies are in the range of 300 kHz and 1 MHz. This high-frequency switching signal has to be removed from the amplified signal by a lowpass filter. Usually a simple first-order lowpass is being utilized. Due to non-linearities of the pulse-width modulator and the switching transistor itself, class-D amps by nature have amongst the highest audio distortion of any audio amplifier.
More recent audio amplifiers incorporate some type of means in order to reduce distortion. One method is to feed back the amplified audio signal to the input of the amp to compare with the original signal. The difference signal is subsequently utilized in order to correct the switching stage and compensate for the nonlinearity. "Class-T" amps (also known as "t-amp") make use of this sort of feedback mechanism and therefore can be manufactured very small whilst attaining small music distortion.
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