Requirements concerning audio power and audio fidelity of recent speakers and home theater products are constantly increasing. At the core of these systems is the audio amp. Today’s mini amps have to perform well enough to satisfy these always growing demands. It is difficult to pick an amplifier given the big number of styles and concepts. I will explain a few of the most common amp designs including “tube amplifiers”, “linear amplifiers”, “class-AB” and “class-D” and also “class-T amplifiers” to help you understand a few of the terms commonly utilized by amplifier suppliers. This guide should also help you figure out what topology is perfect for your particular application.
The basic operating principle of an audio amp is quite basic. An audio amplifier will take a low-level audio signal. This signal usually originates from a source with a comparatively high impedance. It subsequently translates this signal into a large-level signal. This large-level signal may also drive loudspeakers with low impedance. Determined by the type of amplifier, one of several types of elements are utilized in order to amplify the signal like tubes and transistors.
A few decades ago, the most popular type of audio amplifier were tube amps. Tube amps employ 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 transformed into a high-level signal. Tubes, however, are nonlinear in their behavior and are going to introduce a fairly large level of higher harmonics or distortion. Today, tube amps still have a lot of fans. The main reason is that the distortion which tubes cause are often perceived as “warm” or “pleasant”. Solid state amps with low distortion, on the other hand, are perceived as “cold”. Furthermore, tube amps have rather low power efficiency and thereby radiate much power as heat. Tube amps, however, a fairly expensive to manufacture and thus tube amplifiers have mostly been replaced with amps using transistor elements which are less expensive to make.
The first generation models of solid state amplifiers are often known as “Class-A” amps. Solid-state amplifiers utilize a semiconductor rather than a tube to amplify the signal. Typically bipolar transistors or FETs are being used. The working principle of class-A amps is quite similar to that of tube amplifiers. The primary difference is that a transistor is being utilized as opposed to the tube for amplifying the audio signal. The amplified high-level signal is sometimes fed back in order to minimize harmonic distortion. Class-A amps have the smallest distortion and usually also the smallest amount of noise of any amplifier architecture. If you require ultra-low distortion then you should take a closer look at class-A models. Though, similar to tube amplifiers, class-A amps have very low power efficiency and the majority of the power is wasted.
By employing a number of transistors, class-AB amplifiers improve on the low power efficiency of class-A amplifiers. The operating region is split into two separate areas. These 2 regions are handled by separate transistors. Each of those transistors works more efficiently than the single transistor in a class-A amp. The larger efficiency of class-AB amps also has 2 other benefits. First of all, the required number of heat sinking is reduced. For that reason class-AB amplifiers can be manufactured lighter and smaller. For that reason, class-AB amps can be made cheaper than class-A amps. When the signal transitions between the 2 separate areas, though, a certain level of distortion is being created, thereby class-AB amplifiers will not achieve the same audio fidelity as class-A amplifiers.
Class-D amplifiers are able to achieve power efficiencies higher than 90% by utilizing a switching transistor that is constantly being switched on and off and therefore the transistor itself does not dissipate any heat. 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 get back the music signal. Both the pulse-width modulator and the transistor have non-linearities that result in class-D amps exhibiting larger music distortion than other kinds of amplifiers.
New amps include internal audio feedback to minimize the amount of audio distortion. “Class-T” amps (also referred to as “t-amplifier”) make use of this kind of feedback mechanism and for that reason can be manufactured very small while achieving low audio distortion.
Exactly How Do Bluetooth Audio Receivers Can Rival Bluetooth Speakers? 