Requirements regarding audio power and audio fidelity of recent speakers and home theater products are constantly growing. At the core of these systems is the music amplifier. Latest power amps have to perform well enough to satisfy these always increasing demands. It is tough to choose an amplifier given the big number of products and concepts. I will describe a few of the most popular amp designs including "tube amps", "linear amplifiers", "class-AB" and "class-D" along with "class-T amps" to help you understand a few of the terms frequently utilized by amp suppliers. This guide should also help you figure out what topology is ideal for your particular application. The main operating principle of an audio amplifier is fairly basic. An audio amplifier is going to take a low-level audio signal. This signal regularly originates from a source with a rather large impedance. It subsequently translates this signal into a large-level signal. This large-level signal may also drive speakers with small impedance. In order to do that, an amplifier utilizes one or several elements that are controlled by the low-power signal to make a large-power signal. These elements range from tubes, bipolar transistors to FET transistors.
The main operating principle of an audio amp is rather straightforward. An audio amplifier will take a low-level audio signal. This signal regularly comes from a source with a comparatively large impedance. It then translates this signal into a large-level signal. This large-level signal may also drive loudspeakers with low impedance. Determined by the kind of amp, one of several types of elements are utilized to amplify the signal such as tubes in addition to transistors.
Tube amplifiers used to be common several decades ago. A tube is able to control the current flow in accordance to a control voltage that is connected to the tube. One dilemma with tubes is that they are not very linear whilst amplifying signals. Aside from the original music, there will be overtones or higher harmonics present in the amplified signal. Consequently tube amplifiers have rather high distortion. On the other hand, this characteristic of tube amps still makes these popular. A lot of people describe tube amps as having a warm sound versus the cold sound of solid state amps.
Another drawback of tube amps, however, is the small power efficiency. The bulk of power which tube amps consume is being dissipated as heat and merely a portion is being transformed into audio power. Tube amps, however, a quite costly to make and for that reason tube amps have mostly been replaced with amplifiers employing transistor elements which are less expensive to manufacture.
In order to improve on the small efficiency of class-A amps, class-AB amps utilize a series of transistors that each amplify a separate area, each of which being more efficient than class-A amps. Due to the larger efficiency, class-AB amplifiers do not require the same amount of heat sinks as class-A amplifiers. Consequently they can be made lighter and cheaper. Class-AB amplifiers have a downside however. Every time the amplified signal transitions from a region to the other, there will be certain distortion created. In other words the transition between those 2 regions is non-linear in nature. Therefore class-AB amps lack audio fidelity compared with class-A amplifiers.
Class-D amplifiers are able to achieve power efficiencies above 90% by employing a switching transistor that is constantly being switched on and off and as a result the transistor itself does not dissipate any heat. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). Typical switching frequencies are between 300 kHz and 1 MHz. This high-frequency switching signal needs to be removed from the amplified signal by a lowpass filter. Typically a straightforward first-order lowpass is being utilized. The switching transistor and also the pulse-width modulator generally exhibit quite large non-linearities. As a consequence, the amplified signal will have some distortion. Class-D amps by nature have larger audio distortion than other kinds of audio amps.
In order to further improve the audio efficiency, "class-D" amplifiers utilize a switching stage that is continuously switched between two states: on or off. None of these 2 states dissipates power inside the transistor. Consequently, class-D amps regularly are able to achieve power efficiencies beyond 90%. The switching transistor, that is being controlled by a pulse-width modulator generates a high-frequency switching component which needs to be removed from the amplified signal by making use of a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amps exhibiting bigger music distortion than other types of amplifiers. More modern audio amplifiers incorporate some kind of means to reduce distortion. One approach is to feed back the amplified music signal to the input of the amp to compare with the original signal. The difference signal is then utilized to correct the switching stage and compensate for the nonlinearity. A well-known architecture which makes use of this kind of feedback is known as "class-T". Class-T amplifiers or "t amps" attain audio distortion which compares with the audio distortion of class-A amps while at the same time offering the power efficiency of class-D amps. Consequently t amplifiers can be made extremely small and yet achieve high audio fidelity.
The main operating principle of an audio amp is rather straightforward. An audio amplifier will take a low-level audio signal. This signal regularly comes from a source with a comparatively large impedance. It then translates this signal into a large-level signal. This large-level signal may also drive loudspeakers with low impedance. Determined by the kind of amp, one of several types of elements are utilized to amplify the signal such as tubes in addition to transistors.
Tube amplifiers used to be common several decades ago. A tube is able to control the current flow in accordance to a control voltage that is connected to the tube. One dilemma with tubes is that they are not very linear whilst amplifying signals. Aside from the original music, there will be overtones or higher harmonics present in the amplified signal. Consequently tube amplifiers have rather high distortion. On the other hand, this characteristic of tube amps still makes these popular. A lot of people describe tube amps as having a warm sound versus the cold sound of solid state amps.
Another drawback of tube amps, however, is the small power efficiency. The bulk of power which tube amps consume is being dissipated as heat and merely a portion is being transformed into audio power. Tube amps, however, a quite costly to make and for that reason tube amps have mostly been replaced with amplifiers employing transistor elements which are less expensive to manufacture.
In order to improve on the small efficiency of class-A amps, class-AB amps utilize a series of transistors that each amplify a separate area, each of which being more efficient than class-A amps. Due to the larger efficiency, class-AB amplifiers do not require the same amount of heat sinks as class-A amplifiers. Consequently they can be made lighter and cheaper. Class-AB amplifiers have a downside however. Every time the amplified signal transitions from a region to the other, there will be certain distortion created. In other words the transition between those 2 regions is non-linear in nature. Therefore class-AB amps lack audio fidelity compared with class-A amplifiers.
Class-D amplifiers are able to achieve power efficiencies above 90% by employing a switching transistor that is constantly being switched on and off and as a result the transistor itself does not dissipate any heat. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). Typical switching frequencies are between 300 kHz and 1 MHz. This high-frequency switching signal needs to be removed from the amplified signal by a lowpass filter. Typically a straightforward first-order lowpass is being utilized. The switching transistor and also the pulse-width modulator generally exhibit quite large non-linearities. As a consequence, the amplified signal will have some distortion. Class-D amps by nature have larger audio distortion than other kinds of audio amps.
In order to further improve the audio efficiency, "class-D" amplifiers utilize a switching stage that is continuously switched between two states: on or off. None of these 2 states dissipates power inside the transistor. Consequently, class-D amps regularly are able to achieve power efficiencies beyond 90%. The switching transistor, that is being controlled by a pulse-width modulator generates a high-frequency switching component which needs to be removed from the amplified signal by making use of a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amps exhibiting bigger music distortion than other types of amplifiers. More modern audio amplifiers incorporate some kind of means to reduce distortion. One approach is to feed back the amplified music signal to the input of the amp to compare with the original signal. The difference signal is then utilized to correct the switching stage and compensate for the nonlinearity. A well-known architecture which makes use of this kind of feedback is known as "class-T". Class-T amplifiers or "t amps" attain audio distortion which compares with the audio distortion of class-A amps while at the same time offering the power efficiency of class-D amps. Consequently t amplifiers can be made extremely small and yet achieve high audio fidelity.
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