None of modern audio systems would be doable lacking the aid of recent audio amps that strive to satisfy higher and higher requirements regarding power and audio fidelity. There is a large amount of amp designs and models. All of these differ when it comes to performance. I am going to explain some of the most common amp terms such as "class-A", "class-D" and "t amps" to help you figure out which of these amps is ideal for your application. Furthermore, after reading this article you should be able to understand the amp specs that manufacturers publish.

An audio amp will translate a low-level music signal that frequently originates from a high-impedance source into a high-level signal which can drive a loudspeaker with a low impedance. Determined by the kind of amplifier, one of several kinds of elements are utilized to amplify the signal including tubes and transistors.

Tube amps used to be widespread a few decades ago. A tube is able to control the current flow in accordance to a control voltage which is attached to the tube. Tubes, however, are nonlinear in their behavior and are going to introduce a quite large level of higher harmonics or distortion. Though, this characteristic of tube amps still makes these popular. A lot of people describe tube amps as having a warm sound versus the cold sound of solid state amplifiers.

One more drawback of tube amps, however, is the low power efficiency. The bulk of power which tube amps use up is being dissipated as heat and merely a portion is being transformed into audio power. Yet one more disadvantage is the big price tag of tubes. This has put tube amplifiers out of the ballpark for many consumer products. As a result, the majority of audio products these days employs solid state amps. I am going to describe solid state amplifiers in the following paragraphs.

Solid-state amps utilize a semiconductor element, such as a bipolar transistor or FET instead of the tube and the first kind is called "class-A" amps. In class-A amps a transistor controls the current flow according to a small-level signal. Several amps employ a feedback mechanism in order to reduce the harmonic distortion. Class-A amps have the smallest distortion and usually also the lowest amount of noise of any amplifier architecture. If you require ultra-low distortion then you should take a closer look at class-A models. Class-A amplifiers, on the other hand, waste most of the energy as heat. As a result they typically have large heat sinks and are fairly heavy.

In order to improve on the small efficiency of class-A amplifiers, class-AB amplifiers employ a series of transistors that each amplify a distinct area, each of which being more efficient than class-A amplifiers. As such, class-AB amplifiers are generally smaller than class-A amplifiers. Nonetheless, this topology adds some non-linearity or distortion in the area where the signal switches between those regions. As such class-AB amps typically have larger distortion than class-A amps.

In order to further improve the audio efficiency, "class-D" amplifiers make use of a switching stage which is constantly switched between 2 states: on or off. None of these two states dissipates energy within the transistor. Consequently, class-D amplifiers frequently are able to attain power efficiencies beyond 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 utilizing a lowpass filter. Both the pulse-width modulator and the transistor have non-linearities which result in class-D amps having bigger audio distortion than other types of amplifiers.

More modern audio amps include some type of means to reduce distortion. One method is to feed back the amplified music signal to the input of the amplifier to compare with the original signal. The difference signal is then used to correct the switching stage and compensate for the nonlinearity. One kind of audio amps which utilizes this type of feedback is known as "class-T" or "t amp". Class-T amplifiers feed back the high-level switching signal to the audio signal processor for comparison. These amps have small audio distortion and can be made very small.