Stereo amplifiers are at the very center of every home theater system. As the quality and output power demands of modern loudspeakers increase, so do the requirements of power amplifiers. There is a large quantity of amplifier designs and types. All of these vary regarding performance. I am going to describe 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. Moreover, after understanding this essay you should be able to comprehend the amplifier specs that makers issue.
The main operating principle of an audio amp is quite clear-cut. An audio amplifier is going to take a low-level audio signal. This signal generally comes from a source with a comparatively high impedance. It then converts this signal into a large-level signal. This large-level signal may also drive loudspeakers with small impedance. Depending on the type of amplifier, one of several types of elements are used to amplify the signal like tubes and transistors.
Tube amplifiers were frequently used a number of decades ago and employ a vacuum tube that controls a high-voltage signal in accordance to a low-voltage control signal. 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. For that reason tube amps have quite high distortion. Today, tube amps still have a lot of followers. The most important reason is that the distortion that tubes cause are often perceived as “warm” or “pleasant”. Solid state amplifiers with low distortion, on the other hand, are perceived as “cold”. In addition, tube amps have rather low power efficiency and consequently dissipate a lot of power as heat. Tube amps, however, a rather costly to produce and therefore tube amplifiers have by and large been replaced with amps using transistor elements that are less costly to build.
The first generation versions of solid state amps are often known as “Class-A” amps. Solid-state amps employ a semiconductor as opposed to a tube to amplify the signal. Usually bipolar transistors or FETs are being utilized. In class-A amps a transistor controls the current flow according to a small-level signal. Some amps use a feedback mechanism to minimize the harmonic distortion. If you require an ultra-low distortion amp then you may wish to explore class-A amps since they offer amongst the lowest distortion of any mini stereo amps. Class-A amps, though, waste the majority of the energy as heat. Consequently they typically have large heat sinks and are quite bulky. By employing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The operating region 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. Because of the larger efficiency, class-AB amps do not require the same number of heat sinks as class-A amps. For that reason they can be manufactured lighter and less costly. Class-AB amplifiers have a downside however. Each time the amplified signal transitions from one region to the other, there will be certain distortion created. In other words the transition between these 2 regions is non-linear in nature. Consequently class-AB amplifiers lack audio fidelity compared with class-A amplifiers.
Class-D amps are able to attain power efficiencies higher than 90% by using a switching transistor that is continually being switched on and off and thus the transistor itself does not dissipate any heat. The switching transistor, that is being controlled by a pulse-width modulator generates a high-frequency switching component that needs to be removed from the amplified signal by utilizing a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amplifiers exhibiting bigger music distortion than other kinds of amps.
New amplifiers include internal audio feedback in order to reduce the level of audio distortion. “Class-T” amps (also known as “t-amplifier”) employ this sort of feedback method and for that reason can be manufactured very small whilst attaining low audio distortion.
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