A Short Overview Of Power Amps
Audio amplifiers are at the very core of every home theater system. As the quality and output power demands of modern loudspeakers increase, so do the demands of power amps. With the ever increasing amount of models and design topologies, including "tube amplifiers", "class-A", "class-D" in addition to "t amplifier" designs, it is getting more and more difficult to pick the amp that is ideal for a particular application. This post will explain some of the most popular terms and clarify a few of the technical jargon that amplifier makers regularly utilize. Simply put, the principle of an audio amp is to translate a low-power audio signal into a high-power music signal. The high-power signal is big enough to drive a speaker adequately loud. In order to do that, an amp uses one or several elements that are controlled by the low-power signal to produce a large-power signal. These elements range from tubes, bipolar transistors to FET transistors.
The main operating principle of an audio amp is rather clear-cut. An audio amp is going to take a low-level audio signal. This signal usually originates from a source with a rather large impedance. It subsequently translates this signal into a large-level signal. This large-level signal can also drive speakers with low impedance. The type of element used to amplify the signal depends on which amp architecture is used. Several amps even employ several kinds of elements. Generally the following parts are utilized: tubes, bipolar transistors as well as FETs.
Another disadvantage of tube amplifiers, 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 converted 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 products. Consequently, the bulk of audio products today utilizes solid state amps. I am going to describe solid state amplifiers in the subsequent sections.
In addition, tube amplifiers have fairly low power efficiency and therefore radiate much power as heat. Tube amplifiers, on the other hand, a quite expensive to make and thus tube amps have by and large been replaced with amps employing transistor elements which are less expensive to manufacture.
To improve on the low efficiency of class-A amplifiers, class-AB amplifiers make use of a series of transistors which each amplify a separate area, each of which being more efficient than class-A amps. As such, class-AB amps are typically smaller than class-A amps. When the signal transitions between the two separate regions, though, a certain level of distortion is being generated, thus class-AB amps will not achieve the same audio fidelity as class-A amplifiers.
Class-AB amplifiers improve on the efficiency of class-A amps. They employ a number of transistors in order to split up the large-level signals into 2 separate regions, each of which can be amplified more efficiently. As such, class-AB amplifiers are typically smaller than class-A amps. Though, this architecture adds some non-linearity or distortion in the region where the signal switches between those regions. As such class-AB amps typically have higher distortion than class-A amplifiers.
Class-D amplifiers are able to attain power efficiencies above 90% by utilizing a switching transistor that is continuously being switched on and off and as a result the transistor itself does not dissipate any heat. The switching transistor is being controlled by a pulse-width modulator. The switched large-level signal needs to be lowpass filtered to remove the switching signal and recover the music signal. The switching transistor and in addition the pulse-width modulator usually have fairly big non-linearities. As a consequence, the amplified signal will contain some distortion. Class-D amplifiers by nature exhibit larger audio distortion than other types of audio amplifiers. New amplifiers include internal audio feedback in order to reduce the level of music distortion. A well-known architecture that employs this kind of feedback is generally known as "class-T". Class-T amplifiers or "t amps" attain audio distortion that compares with the audio distortion of class-A amps while at the same time offering the power efficiency of class-D amplifiers. Therefore t amplifiers can be made extremely small and yet attain high audio fidelity.
The main operating principle of an audio amp is rather clear-cut. An audio amp is going to take a low-level audio signal. This signal usually originates from a source with a rather large impedance. It subsequently translates this signal into a large-level signal. This large-level signal can also drive speakers with low impedance. The type of element used to amplify the signal depends on which amp architecture is used. Several amps even employ several kinds of elements. Generally the following parts are utilized: tubes, bipolar transistors as well as FETs.
Another disadvantage of tube amplifiers, 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 converted 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 products. Consequently, the bulk of audio products today utilizes solid state amps. I am going to describe solid state amplifiers in the subsequent sections.
In addition, tube amplifiers have fairly low power efficiency and therefore radiate much power as heat. Tube amplifiers, on the other hand, a quite expensive to make and thus tube amps have by and large been replaced with amps employing transistor elements which are less expensive to manufacture.
To improve on the low efficiency of class-A amplifiers, class-AB amplifiers make use of a series of transistors which each amplify a separate area, each of which being more efficient than class-A amps. As such, class-AB amps are typically smaller than class-A amps. When the signal transitions between the two separate regions, though, a certain level of distortion is being generated, thus class-AB amps will not achieve the same audio fidelity as class-A amplifiers.
Class-AB amplifiers improve on the efficiency of class-A amps. They employ a number of transistors in order to split up the large-level signals into 2 separate regions, each of which can be amplified more efficiently. As such, class-AB amplifiers are typically smaller than class-A amps. Though, this architecture adds some non-linearity or distortion in the region where the signal switches between those regions. As such class-AB amps typically have higher distortion than class-A amplifiers.
Class-D amplifiers are able to attain power efficiencies above 90% by utilizing a switching transistor that is continuously being switched on and off and as a result the transistor itself does not dissipate any heat. The switching transistor is being controlled by a pulse-width modulator. The switched large-level signal needs to be lowpass filtered to remove the switching signal and recover the music signal. The switching transistor and in addition the pulse-width modulator usually have fairly big non-linearities. As a consequence, the amplified signal will contain some distortion. Class-D amplifiers by nature exhibit larger audio distortion than other types of audio amplifiers. New amplifiers include internal audio feedback in order to reduce the level of music distortion. A well-known architecture that employs this kind of feedback is generally known as "class-T". Class-T amplifiers or "t amps" attain audio distortion that compares with the audio distortion of class-A amps while at the same time offering the power efficiency of class-D amplifiers. Therefore t amplifiers can be made extremely small and yet attain high audio fidelity.
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