Demands concerning audio power and audio fidelity of latest speakers and home theater systems are always increasing. At the center of these systems is the music amp. Latest audio amps have to perform well enough to meet those ever growing requirements. There is a huge quantity of amp concepts and types. All of these vary when it comes to performance. I am going to explain some of the most popular amplifier terms such as “class-A”, “class-D” and “t amps” to help you figure out which of these amps is ideal for your application. Also, after understanding this article you should be able to understand the amp specifications that manufacturers publish. The basic operating principle of an audio amplifier is fairly basic. An audio amplifier will take a low-level audio signal. This signal usually comes from a source with a fairly high impedance. It subsequently converts this signal into a large-level signal. This large-level signal can also drive loudspeakers with small impedance. Depending on the kind of amp, one of several types of elements are utilized in order to amplify the signal like tubes as well as transistors.
Several decades ago, the most widespread kind of audio amplifier were tube amps. Tube amps make use of 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. Tubes, though, are nonlinear in their behavior and will introduce a fairly large level of higher harmonics or distortion. However, this characteristic of tube amps still makes these popular. Many people describe tube amps as having a warm sound as opposed to the cold sound of solid state amplifiers.
One more drawback of tube amplifiers, though, is the low power efficiency. The majority of power which tube amplifiers use up is being dissipated as heat and only a part is being converted into audio power. Tube amps, on the other hand, a quite expensive to make and as a result tube amps have by and large been replaced with amps utilizing transistor elements that are less costly to produce. Solid-state amplifiers employ a semiconductor element, such as a bipolar transistor or FET as opposed to the tube and the first sort is often known as “class-A” amps. 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 as opposed to the tube for amplifying the music signal. The amplified high-level signal is sometimes fed back to minimize harmonic distortion. If you require an ultra-low distortion amplifier then you might wish to explore class-A amplifiers as they provide amongst the smallest distortion of any audio amplifiers. The main downside is that much like tube amps class A amplifiers have extremely small efficiency. As a result these amplifiers need large heat sinks in order to dissipate the wasted energy and are usually fairly heavy.
In order to improve on the low 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. As such, class-AB amplifiers are generally smaller than class-A amplifiers. Class-AB amplifiers have a disadvantage however. Every time the amplified signal transitions from a region to the other, there will be some distortion generated. In other words the transition between those 2 areas is non-linear in nature. As a result class-AB amplifiers lack audio fidelity compared with class-A amps.
In order to further improve the audio efficiency, “class-D” amps employ a switching stage that is constantly switched between two states: on or off. None of these 2 states dissipates energy within the transistor. Consequently, class-D amplifiers frequently are able to achieve power efficiencies beyond 90%. 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 audio signal. The switching transistor and also the pulse-width modulator frequently exhibit rather big non-linearities. As a consequence, the amplified signal is going to contain some distortion. Class-D amps by nature exhibit larger audio distortion than other types of audio amps.
New amps incorporate internal audio feedback to minimize the amount of music distortion. “Class-T” amps (also known as “t-amp”) make use of this sort of feedback method and for that reason can be manufactured extremely small while achieving small audio distortion.
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