A Short Introduction Of Power Amps

Stereo amps are at the very center of each home theater system. As the quality and output power demands of today’s speakers increase, so do the requirements of stereo amplifiers. There is a big amount of amplifier concepts and types. All of these differ in terms of performance. I am going to describe some of the most common amp terms like “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 essay you should be able to comprehend the amp specifications which suppliers issue. Simply put, the principle of an audio amplifier is to convert a low-power audio signal into a high-power music signal. The high-power signal is big enough to drive a speaker adequately loud. Depending on the kind of amplifier, one of several types of elements are used in order to amplify the signal like tubes in addition to transistors.

A number of decades ago, the most widespread kind of audio amp were tube amplifiers. Tube amps utilize a tube as the amplifying element. The current flow through the tube is controlled by a low-level control signal. Thereby the low-level audio is converted into a high-level signal. One drawback with tubes is that they are not extremely linear when amplifying signals. Aside from the original audio, there will be overtones or higher harmonics present in the amplified signal. Hence tube amplifiers have moderately high distortion. Many people prefer tube amps since those higher harmonics are often perceived as the tube amp sounding “warm” or “pleasant”.

In addition, tube amplifiers have fairly low power efficiency and as a result radiate a lot of power as heat. Tube amplifiers, though, a quite costly to manufacture and as a result tube amplifiers have by and large been replaced with amplifiers utilizing transistor elements that are less expensive to build. Solid-state amps utilize a semiconductor element, like a bipolar transistor or FET instead of the tube and the earliest type is often known as “class-A” amps. In a class-A amp, the signal is being amplified by a transistor which is controlled by the low-level audio signal. If you need an ultra-low distortion amp then you might want to investigate class-A amps since they offer amongst the smallest distortion of any audio amplifiers. Class-A amps, however, waste the majority of the power as heat. Therefore they frequently have big heat sinks and are quite bulky.

By employing a number of transistors, class-AB amplifiers improve on the low power efficiency of class-A amps. The operating region is split into 2 separate areas. These 2 regions are handled by separate transistors. Each of these transistors works more efficiently than the single transistor in a class-A amp. As such, class-AB amps are generally smaller than class-A amps. When the signal transitions between the two distinct areas, though, a certain amount of distortion is being produced, thus class-AB amps will not achieve the same audio fidelity as class-A amps.

Class-D amps improve on the efficiency of class-AB amps even further by employing a switching transistor that is continuously being switched on or off. Thus this switching stage hardly dissipates any energy and therefore the power efficiency of class-D amps generally surpasses 90%. The switching transistor, which is being controlled by a pulse-width modulator generates a high-frequency switching component which has to be removed from the amplified signal by making use of a lowpass filter. 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.

To resolve the dilemma of high music distortion, modern switching amp styles incorporate feedback. The amplified signal is compared with the original low-level signal and errors are corrected. One kind of small stereo amps which utilizes this kind of feedback is called “class-T” or “t amplifier”. Class-T amps feed back the high-level switching signal to the audio signal processor for comparison. These amps exhibit small music distortion and can be manufactured very small.


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