None of recent stereo products would be achievable lacking the help of latest audio amplifiers which try to satisfy higher and higher requirements concerning power and audio fidelity. With the ever increasing amount of models and design topologies, such as "tube amplifiers", "class-A", "class-D" along with "t amp" types, it is getting more and more complex to choose the amplifier that is perfect for a particular application. This guide will describe some of the most popular terms and clarify some of the technical jargon which amplifier manufacturers frequently employ.
The basic operating principle of an audio amp is quite clear-cut. An audio amp will take a low-level music signal. This signal regularly comes from a source with a fairly high impedance. It subsequently converts this signal into a large-level signal. This large-level signal may also drive speakers with low impedance. Determined by the type of amplifier, one of several types of elements are used to amplify the signal like tubes and transistors.
Besides, tube amplifiers have rather low power efficiency and as a result dissipate much power as heat. Furthermore, tubes are fairly costly to produce. Consequently tube amplifiers have by and large been replaced by solid-state amplifiers which I will glance at next.
One downside of tube amps is their low power efficiency. In other words, most of the power consumed by the amplifier is wasted as heat rather than being converted into music. For that reason tube amplifiers will run hot and require adequate cooling. Yet another downside is the high price tag of tubes. This has put tube amplifiers out of the ballpark for many consumer products. Consequently, the bulk of audio products nowadays makes use of solid state amps. I am going to explain solid state amps in the following paragraphs.
By utilizing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The working area is divided into two separate areas. These two areas are handled by separate transistors. Each of these transistors operates more efficiently than the single transistor in a class-A amplifier. As a result of the higher efficiency, class-AB amplifiers do not need the same amount of heat sinks as class-A amps. Consequently they can be made lighter and less expensive. However, this topology adds some non-linearity or distortion in the area where the signal switches between those areas. As such class-AB amps typically have larger distortion than class-A amplifiers.
In order to further improve the audio efficiency, "class-D" amplifiers make use of a switching stage that is continually switched between 2 states: on or off. None of these 2 states dissipates power inside the transistor. Therefore, class-D amplifiers frequently are able to attain power efficiencies beyond 90%. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). Usual switching frequencies are between 300 kHz and 1 MHz. This high-frequency switching signal has to be removed from the amplified signal by a lowpass filter. Usually a simple first-order lowpass is being used. Both the pulse-width modulator and the transistor have non-linearities that result in class-D amps having larger audio distortion than other types of amplifiers.
Class-D amplifiers improve on the efficiency of class-AB amplifiers even further by making use of a switching transistor that is continuously being switched on or off. Thereby this switching stage barely dissipates any power and thereby the power efficiency of class-D amps usually surpasses 90%. The switching transistor, that is being controlled by a pulse-width modulator generates a high-frequency switching component which needs to be removed from the amplified signal by utilizing 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 highest audio distortion of any audio amplifier. More modern audio amplifiers include some kind of mechanism to reduce distortion. One method is to feed back the amplified music signal to the input of the amplifier in order to compare with the original signal. The difference signal is subsequently used in order to correct the switching stage and compensate for the nonlinearity. One kind of audio amps that utilizes this kind of feedback is known as "class-T" or "t amplifier". Class-T amps feed back the high-level switching signal to the audio signal processor for comparison. These amplifiers have low music distortion and can be made extremely small.
The basic operating principle of an audio amp is quite clear-cut. An audio amp will take a low-level music signal. This signal regularly comes from a source with a fairly high impedance. It subsequently converts this signal into a large-level signal. This large-level signal may also drive speakers with low impedance. Determined by the type of amplifier, one of several types of elements are used to amplify the signal like tubes and transistors.
Besides, tube amplifiers have rather low power efficiency and as a result dissipate much power as heat. Furthermore, tubes are fairly costly to produce. Consequently tube amplifiers have by and large been replaced by solid-state amplifiers which I will glance at next.
One downside of tube amps is their low power efficiency. In other words, most of the power consumed by the amplifier is wasted as heat rather than being converted into music. For that reason tube amplifiers will run hot and require adequate cooling. Yet another downside is the high price tag of tubes. This has put tube amplifiers out of the ballpark for many consumer products. Consequently, the bulk of audio products nowadays makes use of solid state amps. I am going to explain solid state amps in the following paragraphs.
By utilizing a series of transistors, class-AB amps improve on the small power efficiency of class-A amplifiers. The working area is divided into two separate areas. These two areas are handled by separate transistors. Each of these transistors operates more efficiently than the single transistor in a class-A amplifier. As a result of the higher efficiency, class-AB amplifiers do not need the same amount of heat sinks as class-A amps. Consequently they can be made lighter and less expensive. However, this topology adds some non-linearity or distortion in the area where the signal switches between those areas. As such class-AB amps typically have larger distortion than class-A amplifiers.
In order to further improve the audio efficiency, "class-D" amplifiers make use of a switching stage that is continually switched between 2 states: on or off. None of these 2 states dissipates power inside the transistor. Therefore, class-D amplifiers frequently are able to attain power efficiencies beyond 90%. The on-off switching times of the transistor are being controlled by a pulse-with modulator (PWM). Usual switching frequencies are between 300 kHz and 1 MHz. This high-frequency switching signal has to be removed from the amplified signal by a lowpass filter. Usually a simple first-order lowpass is being used. Both the pulse-width modulator and the transistor have non-linearities that result in class-D amps having larger audio distortion than other types of amplifiers.
Class-D amplifiers improve on the efficiency of class-AB amplifiers even further by making use of a switching transistor that is continuously being switched on or off. Thereby this switching stage barely dissipates any power and thereby the power efficiency of class-D amps usually surpasses 90%. The switching transistor, that is being controlled by a pulse-width modulator generates a high-frequency switching component which needs to be removed from the amplified signal by utilizing 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 highest audio distortion of any audio amplifier. More modern audio amplifiers include some kind of mechanism to reduce distortion. One method is to feed back the amplified music signal to the input of the amplifier in order to compare with the original signal. The difference signal is subsequently used in order to correct the switching stage and compensate for the nonlinearity. One kind of audio amps that utilizes this kind of feedback is known as "class-T" or "t amplifier". Class-T amps feed back the high-level switching signal to the audio signal processor for comparison. These amplifiers have low music distortion and can be made extremely small.
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