Demands regarding audio power and audio fidelity of todays speakers and home theater products are always increasing. At the center of those products is the music amplifier. With the ever growing number of models and design topologies, like “tube amplifiers”, “class-A”, “class-D” and “t amp” types, it is getting more and more complex to pick the amp that is best for a particular application. Simply put, the purpose of an audio amplifier is to convert a low-power music signal into a high-power audio signal. Solid state amps with low distortion, on the other hand, are perceived as “cold”.
One drawback of tube amplifiers is their low power efficiency. Hence tube amplifiers have by and large been replaced by solid-state amps which I am going to glance at next.
In a class-A amplifier, the signal is being amplified by a transistor which is controlled by the low-level audio signal. As such class-A amplifiers are ideal for very demanding applications in which low distortion and low noise are essential. By using a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The operating area is divided into 2 separate regions. As such class-AB amps normally have higher distortion than class-A mini ampsmini amps.
Class-D amplifiers improve on the efficiency of class-AB amps even further by using a switching transistor that is constantly being switched on or off. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). This high-frequency switching signal has to be removed from the amplified signal by a lowpass filter. As a consequence, the amplified signal is going to contain some distortion. Class-D amps by nature have larger audio distortion than other types of audio amps. Newer amps incorporate internal audio feedback in order to reduce the level of music distortion. “Class-T” amplifiers (also called “t-amplifier”) utilize this kind of feedback mechanism and for that reason can be made extremely small whilst attaining small music distortion.