An audio power amplifier (or power amp ) is an electronic amplifier that reproduces low-power electronic audio signals such as a signal from a radio receiver or an electric guitar pickup at a level strong enough to drive ( or turn on) loudspeakers or headphones. These include amplifiers used in home audio systems and amplifiers of musical instruments such as guitar amplifiers. This is the last electronic stage in a typical audio playback chain before the signal is sent to the loudspeaker and the enclosure speaker.
The earlier stages in such chains are low power audio amplifiers that perform tasks such as signal pre-amplification (these are mainly related to turntable signals, microphone signals and electrical instrument signals from pickups, such as electric guitars and electric bass), equalization (eg, adjusting bass and treble), tone control, mixing different input signals or adding electronic effects like reverb. Inputs can also be any number of audio sources such as record player, CD player, digital audio player, and cassette player. Most audio power amplifiers require this low-level input, which is the channel level.
While the input signal to an audio power amplifier, such as a signal from an electric guitar, can measure only a few hundred microwatt, its output may be several watts for small consumer electronic devices, such as clock radios, tens or hundreds of watts for home stereo systems, several thousand watts for sound systems nightclubs or tens of thousands of watts for the sound reinforcement system of big rock concerts. While power amplifiers are available in standalone units, usually intended for hi-fi audiophile market (niche market) audio enthusiasts and professional sound reinforcement systems, most consumer electronics sound products, such as clock radios, boom boxes and televisions have relatively small integrated power amplifiers in the main product chassis.
Video Audio power amplifier
Histori
The audio amplifier was invented around 1912 by Lee De Forest, made possible by the invention of the first practical amplifier electrical component, a triode vacuum tube (or "valve" in English English) in 1907. Triode is a three-terminal device with a control network that can modulate the flow electrons from filaments to plates. The triode vacuum amplifier is used to make the first AM radio. Early audio power amplifiers are based on vacuum tubes and some of them achieve very high audio quality (eg, Williamson 1947-9). The audio power amplifier based on transistors became practical with the wide availability of cheap transistors in the late 1960s. Since the 1970s, most modern audio amplifiers are based on solid state devices (transistors such as BJT, FET and MOSFET). Transistor-based amplifiers are lighter, more reliable and require less maintenance than tube amplifiers. In the 2010s, there were still audio fans, musicians (especially electric guitarists, electric bassists, Hammond organ players and electric pianos Fender Rhodes, among others), audio engineers and music producers who preferred tube-based amplifiers, and what was perceived as "warm" tube sound.
Maps Audio power amplifier
Design parameters
The main design parameters for audio power amplifiers are frequency response, gain, noise, and distortion. It is interdependent; increased gain often leads to increased noise and unwanted distortion. While negative feedback actually reduces the gain, it also reduces distortion. Most audio amplifiers are linear amplifiers that operate in class AB.
Until the 1970s, most amplifiers were tube amplifiers that used vacuum tubes. During the 1970s, ampere tubes were increasingly replaced by transistor-based amplifiers, which were lighter, more reliable, and lower maintenance. Nevertheless, there are still consumer market niches that continue to use tube amplifiers and preamplifiers tubes in 2010, such as with hi-fi fans at home, audio engineers and music producers (who use preamplifiers tubes in studio recordings to "heat up" the signal microphone) and electric guitarist, electric bassist and Hammond organ player, among whom minorities continue to use tube preamps, tube power amps and tube effect units. While hi-fi fans and audio engineers perform live sound or monitor tracks in the studio usually look for amplifiers with the lowest distortion, electric instrument players in genres like blues, rock music and heavy metal music, among others, use tube amplifiers because they are like natural overdrive generated ampere tube when pushed hard.
In the 2000s, Class-D amplifiers, much more efficient than Class AB amplifiers, were widely used in consumer electronic audio products, bass amplifiers and sound reinforcement systems, as Class D amplifiers were much lighter and produced less heat.
Filter and preamplifier
Because modern digital devices, including CD and DVD players, radio receivers, and tape decks already provide "flat" signals at the line level, no preamp is required other than as volume control and source selector. One alternative to a separate preamp is to use only passive volume and switching controls, sometimes integrated into a power amplifier to form an integrated amplifier.
Power output stage
The final stage of amplification, after preamplifiers, is the output stage, where the highest demands are placed on transistors or tubes. For this reason, design options are made around the output device (for single-ended output stages, such as single-ended triode amplifiers) or devices (for push-pull output stage), such as the operating class of output devices are often taken as descriptions of the whole power amplifier. For example, Class B amplifiers may only have high-output power devices that are cut off half of each cycle, whereas other devices (such as differential amplifiers, voltage amplifiers and even driver transistors) operate in Class A. In a transformerless output stage, the device is basically in series with power supplies and output loads (such as loudspeakers), perhaps through some large capacitors and/or small resistances.
Further developments
For several years after the introduction of solid state amplifiers, the perceived sound does not have excellent audio quality from the best valve booster (see valve audio amplifier). This causes the audiophile to believe that the "tube sound" or sound of the valve has intrinsic qualities due to the vacuum tube technology itself. In 1970 Matti Otala published a paper on the origin of previously unobserved distortion: transient intermodulation distortion (TIM), then also called slew-induced distortion (SID) by others. TIM distortion is found to occur during the very fast increase of the amplifier voltage.
TIM does not appear on steady state sine tone measurements, helping to hide it from design engineers before 1970. The problem with TIM distortion comes from the reduction of the open loop frequency response of solid state amplifiers. Further works of Otala and other authors found solutions for TIM distortion, including increasing the slew rate, reducing the frequency bandwidth of the preamp, and insertion of the lag compensation circuit in the input amplifier stage. In high quality modern amplifiers, open loop responses are at least 20 kHz, undoing TIM distortion.
The next step in advanced design is the Baxandall Theorem, made by Peter Baxandall in England. This theorem introduces the concept of ratio comparison between input distortion and amplifier output distortion. This new idea helps audio design engineers to better evaluate distortion processes in amplifiers.
Apps
Important applications include public address systems, theater and concert sound reinforcement systems, and domestic systems such as stereo systems or home theaters. Amplifier instruments including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers. In some cases, power amplifiers for instrument boosters are integrated into a single amplifier "head" which contains preamplifiers, tone controls, and electronic effects. These components can be mounted in the wooden speaker cabinet to create a "combo amplifier". Musicians with unique performance requirements and/or the need for very strong amplification can make special arrangements with separate preamplifiers, equalizer, and power amplifiers mounted on a 19 "road case.
Power amplifiers are available in standalone units, used by hi-fi audio enthusiasts and public address system designers (PA systems) and sound reinforcement systems. Users of a hi-fi power amplifier amplifier may have a stereo power amplifier to direct the left and right speakers and a single "monoblock" power amplifier to drive the subwoofer. The number of power boosts used in sound reinforcement settings depends on the size of the place. A small coffee shop may have a single power amplifier that drives two PA speakers. A nightclub may have multiple power amplifiers for the main speakers, one or more power amps for the monitor speakers (pointing towards the band) and an additional power amp for the subwoofer. The stadium concert may have a large amount of power amps mounted on the shelf. Most consumer electronics sound products, such as TVs, boom boxes, home cinema sound systems, Casio and Yamaha electronic keyboards, "combo" guitar amplifiers and car stereos have power amplifiers integrated in the main product chassis.
References
See also
- Triode single-ended
- Tone control circuit
- Push-pull output
- Instrument amplifier (amplifier for musical instrument)
Source of the article : Wikipedia
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