Audio amps are at the very center of every home theater system. As the quality and output power requirements of today's speakers increase, so do the demands of stereo amps. There is a large amount of amp designs and models. All of these differ when it comes to performance. I will explain some of the most common amp terms such as "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 specs that producers publish.
Simply put, the purpose of an audio amp is to convert a low-power music signal into a high-power audio signal. The high-power signal is great enough to drive a loudspeaker adequately loud. Determined by the type of amp, one of several types of elements are utilized to amplify the signal such as tubes and transistors.
Tube amplifiers used to be widespread several decades ago. A tube is able to control the current flow according to a control voltage that is attached to the tube. Regrettably, tube amps have a somewhat high amount of distortion. Technically speaking, tube amplifiers are going to introduce higher harmonics into the signal. On the other hand, this characteristic of tube amps still makes these popular. Many people describe tube amplifiers as having a warm sound versus the cold sound of solid state amps. One more downside of tube amps, however, is the low power efficiency. The majority of power which tube amps consume is being dissipated as heat and merely a part is being transformed into audio power. Also, tubes are quite costly to manufacture. Consequently tube amps have mostly been replaced by solid-state amps which I am going to glance at next.
The first generation types of solid state amplifiers are generally known as "Class-A" amps. Solid-state amplifiers utilize a semiconductor as opposed to a tube to amplify the signal. Generally bipolar transistors or FETs are being used. The working principle of class-A amps is quite similar to that of tube amps. The primary difference is that a transistor is being used in place of the tube for amplifying the audio signal. The amplified high-level signal is sometimes fed back in order to reduce harmonic distortion. In terms of harmonic distortion, class-A amps rank highest among all kinds of audio amps. These amplifiers also typically exhibit quite low noise. As such class-A amplifiers are ideal for very demanding applications in which low distortion and low noise are vital. The major downside is that similar to tube amps class A amps have very small efficiency. Because of this these amps need large heat sinks to dissipate the wasted energy and are frequently rather bulky.
By making use of a number of transistors, class-AB amps improve on the low power efficiency of class-A amps. The working area is split into two distinct areas. These two regions are handled by separate transistors. Each of these transistors works more efficiently than the single transistor in a class-A amplifier. As such, class-AB amplifiers are typically smaller than class-A amps. When the signal transitions between the 2 separate regions, however, a certain level of distortion is being created, thereby class-AB amps will not achieve the same audio fidelity as class-A amplifiers.
Class-D amps are able to attain power efficiencies higher than 90% by employing a switching transistor that is constantly 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 in order to remove the switching signal and get back the music signal. Due to non-linearities of the pulse-width modulator and the switching transistor itself, class-D amps by nature have amongst the largest audio distortion of any audio amplifier.
More modern audio amplifiers include some sort of means to minimize distortion. One method is to feed back the amplified music signal to the input of the amp to compare with the original signal. The difference signal is subsequently used in order to correct the switching stage and compensate for the nonlinearity. "Class-T" amplifiers (also referred to as "t-amp") use this type of feedback method and for that reason can be made extremely small while achieving low music distortion.
Simply put, the purpose of an audio amp is to convert a low-power music signal into a high-power audio signal. The high-power signal is great enough to drive a loudspeaker adequately loud. Determined by the type of amp, one of several types of elements are utilized to amplify the signal such as tubes and transistors.
Tube amplifiers used to be widespread several decades ago. A tube is able to control the current flow according to a control voltage that is attached to the tube. Regrettably, tube amps have a somewhat high amount of distortion. Technically speaking, tube amplifiers are going to introduce higher harmonics into the signal. On the other hand, this characteristic of tube amps still makes these popular. Many people describe tube amplifiers as having a warm sound versus the cold sound of solid state amps. One more downside of tube amps, however, is the low power efficiency. The majority of power which tube amps consume is being dissipated as heat and merely a part is being transformed into audio power. Also, tubes are quite costly to manufacture. Consequently tube amps have mostly been replaced by solid-state amps which I am going to glance at next.
The first generation types of solid state amplifiers are generally known as "Class-A" amps. Solid-state amplifiers utilize a semiconductor as opposed to a tube to amplify the signal. Generally bipolar transistors or FETs are being used. The working principle of class-A amps is quite similar to that of tube amps. The primary difference is that a transistor is being used in place of the tube for amplifying the audio signal. The amplified high-level signal is sometimes fed back in order to reduce harmonic distortion. In terms of harmonic distortion, class-A amps rank highest among all kinds of audio amps. These amplifiers also typically exhibit quite low noise. As such class-A amplifiers are ideal for very demanding applications in which low distortion and low noise are vital. The major downside is that similar to tube amps class A amps have very small efficiency. Because of this these amps need large heat sinks to dissipate the wasted energy and are frequently rather bulky.
By making use of a number of transistors, class-AB amps improve on the low power efficiency of class-A amps. The working area is split into two distinct areas. These two regions are handled by separate transistors. Each of these transistors works more efficiently than the single transistor in a class-A amplifier. As such, class-AB amplifiers are typically smaller than class-A amps. When the signal transitions between the 2 separate regions, however, a certain level of distortion is being created, thereby class-AB amps will not achieve the same audio fidelity as class-A amplifiers.
Class-D amps are able to attain power efficiencies higher than 90% by employing a switching transistor that is constantly 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 in order to remove the switching signal and get back the music signal. Due to non-linearities of the pulse-width modulator and the switching transistor itself, class-D amps by nature have amongst the largest audio distortion of any audio amplifier.
More modern audio amplifiers include some sort of means to minimize distortion. One method is to feed back the amplified music signal to the input of the amp to compare with the original signal. The difference signal is subsequently used in order to correct the switching stage and compensate for the nonlinearity. "Class-T" amplifiers (also referred to as "t-amp") use this type of feedback method and for that reason can be made extremely small while achieving low music distortion.
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