By Gerald O'Brian
None of latest audio systems would be possible lacking the help of recent power amps which try to satisfy higher and higher requirements regarding power and music fidelity. It is challenging to pick an amp given the big range of types and concepts. I am going to explain a few of the most popular amplifier designs like "tube amplifiers", "linear amplifiers", "class-AB" and "class-D" in addition to "class-T amplifiers" to help you comprehend a few of the terms regularly used by amplifier makers. This article should also help you figure out what topology is ideal for your precise application.
The basic operating principle of an audio amp is quite simple. An audio amp is going to take a low-level music signal. This signal generally comes from a source with a fairly high impedance. It subsequently converts this signal into a large-level signal. This large-level signal may also drive loudspeakers with small impedance. The sort of element used to amplify the signal is dependent on which amplifier topology is used. A few amplifiers even use several types of elements. Typically the following parts are utilized: tubes, bipolar transistors as well as FETs.
The basic operating principle of an audio amp is quite simple. An audio amp is going to take a low-level music signal. This signal generally comes from a source with a fairly high impedance. It subsequently converts this signal into a large-level signal. This large-level signal may also drive loudspeakers with small impedance. The sort of element used to amplify the signal is dependent on which amplifier topology is used. A few amplifiers even use several types of elements. Typically the following parts are utilized: tubes, bipolar transistors as well as FETs.
Several decades ago, the most widespread type of audio amp were tube amplifiers. Tube amps employ 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 drawback with tubes is that they are not extremely linear whilst amplifying signals. Aside from the original audio, there will be overtones or higher harmonics present in the amplified signal. As a result tube amplifiers have quite high distortion. On the other hand, this characteristic of tube amplifiers still makes these popular. Many people describe tube amps as having a warm sound versus the cold sound of solid state amps. One disadvantage of tube amplifiers is their low power efficiency. In other words, the majority of the power consumed by the amp is wasted as heat instead of being transformed into audio. Therefore tube amps are going to run hot and need enough cooling. Tube amplifiers, on the other hand, a quite expensive to make and consequently tube amps have by and large been replaced with amps making use of transistor elements which are less expensive to make.
A different downside of tube amps, however, is the low power efficiency. The majority of power which tube amplifiers consume is being dissipated as heat and only a part is being converted into audio power. Tube amplifiers, however, a fairly costly to produce and thus tube amplifiers have by and large been replaced with amps employing transistor elements that are less costly to produce.
By utilizing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The operating area is divided into two distinct regions. These two regions are handled by separate transistors. Each of those transistors operates more efficiently than the single transistor in a class-A amplifier. As such, class-AB amps are generally smaller than class-A amplifiers. When the signal transitions between the 2 distinct areas, however, some amount of distortion is being produced, thereby class-AB amplifiers will not achieve the same audio fidelity as class-A amps.
Class-D amplifiers are able to attain power efficiencies above 90% by employing a switching transistor that is continually being switched on and off and therefore the transistor itself does not dissipate any heat. The switching transistor is being controlled by a pulse-width modulator. The switched large
A different downside of tube amps, however, is the low power efficiency. The majority of power which tube amplifiers consume is being dissipated as heat and only a part is being converted into audio power. Tube amplifiers, however, a fairly costly to produce and thus tube amplifiers have by and large been replaced with amps employing transistor elements that are less costly to produce.
By utilizing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The operating area is divided into two distinct regions. These two regions are handled by separate transistors. Each of those transistors operates more efficiently than the single transistor in a class-A amplifier. As such, class-AB amps are generally smaller than class-A amplifiers. When the signal transitions between the 2 distinct areas, however, some amount of distortion is being produced, thereby class-AB amplifiers will not achieve the same audio fidelity as class-A amps.
Class-D amplifiers are able to attain power efficiencies above 90% by employing a switching transistor that is continually being switched on and off and therefore the transistor itself does not dissipate any heat. The switching transistor is being controlled by a pulse-width modulator. The switched large
A different downside of tube amps, however, is the low power efficiency. The majority of power which tube amplifiers consume is being dissipated as heat and only a part is being converted into audio power. Tube amplifiers, however, a fairly costly to produce and thus tube amplifiers have by and large been replaced with amps employing transistor elements that are less costly to produce.
By utilizing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The operating area is divided into two distinct regions. These two regions are handled by separate transistors. Each of those transistors operates more efficiently than the single transistor in a class-A amplifier. As such, class-AB amps are generally smaller than class-A amplifiers. When the signal transitions between the 2 distinct areas, however, some amount of distortion is being produced, thereby class-AB amplifiers will not achieve the same audio fidelity as class-A amps.
Class-D amplifiers are able to attain power efficiencies above 90% by employing a switching transistor that is continually being switched on and off and therefore the transistor itself does not dissipate any heat. The switching transistor is being controlled by a pulse-width modulator. The switched large-level signal has to be lowpass filtered to remove the switching signal and recover the audio signal. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amplifiers having larger audio distortion than other types of amplifiers.
More modern audio amps include some type of mechanism to reduce distortion. One method is to feed back the amplified audio signal to the input of the amplifier to compare with the original signal. The difference signal is subsequently utilized to correct the switching stage and compensate for the nonlinearity. One kind of audio amplifiers that uses this type of feedback is called "class-T" or "t amp". Class-T amplifiers feed back the high-level switching signal to the audio signal processor for comparison. These amps have small music distortion and can be made extremely small.
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By utilizing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The operating area is divided into two distinct regions. These two regions are handled by separate transistors. Each of those transistors operates more efficiently than the single transistor in a class-A amplifier. As such, class-AB amps are generally smaller than class-A amplifiers. When the signal transitions between the 2 distinct areas, however, some amount of distortion is being produced, thereby class-AB amplifiers will not achieve the same audio fidelity as class-A amps.
Class-D amplifiers are able to attain power efficiencies above 90% by employing a switching transistor that is continually being switched on and off and therefore the transistor itself does not dissipate any heat. The switching transistor is being controlled by a pulse-width modulator. The switched large-level signal has to be lowpass filtered to remove the switching signal and recover the audio signal. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amplifiers having larger audio distortion than other types of amplifiers.
More modern audio amps include some type of mechanism to reduce distortion. One method is to feed back the amplified audio signal to the input of the amplifier to compare with the original signal. The difference signal is subsequently utilized to correct the switching stage and compensate for the nonlinearity. One kind of audio amplifiers that uses this type of feedback is called "class-T" or "t amp". Class-T amplifiers feed back the high-level switching signal to the audio signal processor for comparison. These amps have small music distortion and can be made extremely small.
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