A short guide to understanding audio amplifiers

A short guide to understanding audio amplifiers

Sound amplifiers are at the heart of every home theater system. As the demands of todays speakers increase the quality and power, the requirements of sound amplifiers require. It is difficult to choose an amplifier with the large number of models and designs. I will explain some of the most common amplifier constructions such as tube amplifiers, linear amps,class-AB and class D and class-amps to help you understand some of the terms usually used by amplifier manufacturers . This guide will also help you find out which topology is ideal for your particular application.

Simply put, the purpose of an audio amplifier is to convert a low-power audio signal into a high-power audio signal. The high power signal is large enough to drive a loudspeaker enough high. To do that, an amplifier uses one or more elements controlled by the low power signal to generate a large power signal. These elements range from tubes, bipolar transistors to FET transistors.

Pipe amplifiers used to be common a few decades ago. A tube can control the current flow according to a control voltage that is connected to the tube. Unfortunately, tube amplifiers have quite a large amount of distortion. Technically, tube amplifiers will introduce higher harmonics in the signal. However, this feature of tube amplifiers still makes these popular. Many describe tube amplifiers as a hot sound compared to the cold sound of solid state amps.

Another disadvantage of tube amplifiers, however, is low power efficiency. Most of the power used by the tube amplifier disappears as heat and only one fraction is converted to sound power. Also pipes are quite expensive to do. Pipe amplifiers have thus been replaced by solid state amps as I will look at the next one.

Solid State Amps replace the tube with semiconductor elements, usually bipolar transistors or FET. The earliest type of solid state amps is known as Class A amps. In the Class A amps, a transistor controls the current flow according to a small signal signal. Some amplifiers use a feedback mechanism to minimize harmonic distortion. Class A amplifiers have the lowest distortion and usually also the lowest amount of noise of any amplifier karma. If you need extremely low distortion, take a closer look at class A models. The main downside is that similar Amps in Class A amplifiers have very low efficiency. As a result, these amplifiers require large heat sinks to let go of the wasted energy and are usually quite bulky.

Class-AB amps improve the efficiency of Class A amps. They use a series of transistors to break up the size signals into two separate areas, each of which can be amplified more effectively. As such, class AB amps are usually less than Class A amps. This topology, however, adds some non-linearity or distortion in the region where the signal alternates between these areas. As such, class-AB amps usually have higher distortion than class A amps.

Class D amplifiers further enhance the efficiency of the Class AB amps by using a switching transistor that is constantly turned on or off. Thus, this switching step hardly disappears, and thus the effect of Class D amps usually exceeds 90%. The switching transistor is controlled by a pulse width modulator. The switched live signal must be low pass filtered to remove the acoustic signal and reset the audio signal. Due to nonlinearities of the pulse width modulator and the switching transistor itself, class D ampoure of course has the highest noise distortion of any audio amplifier.

To solve the problem of high noise distortion, newer switch amplifiers contain pattern feedback. The amplified signal is compared to the original low level signal and errors are corrected. A well-known architecture that uses this type of feedback is called class-T. Class T amps or t amps achieve noise distortion that compares with Class A amps noise distortion, while providing the same power as Class D amps. Thus, t-amps can be made extremely small and still achieve high audio reliability.



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