How Do You Know When an Audio Tube in a Stereo Amp Needs to Be Replaced

March 11, 2022 Post a Comment

Sound amplifier with ability output sufficient to drive a loudspeaker

Audio stereo power amplifier made by Unitra

The internal view of a Mission Cyrus 1 Hi Fi integrated audio amplifier (1984)^[1]

An audio power amplifier (or power amp) is an electronic amplifier that amplifies low-ability electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of audio systems including sound reinforcement, public address and dwelling house audio systems and musical musical instrument amplifiers like guitar amplifiers. Information technology is the last electronic phase in a typical audio playback chain before the signal is sent to the loudspeakers.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification of the signal (this is particularly associated with record turntable signals, microphone signals and electric instrument signals from pickups, such as the electric guitar and electric bass), equalization (east.g., adjusting the bass and treble), tone controls, mixing different input signals or adding electronic furnishings such every bit reverb. The inputs can also exist any number of sound sources like record players, CD players, digital audio players and cassette players. Most audio power amplifiers require these low-level inputs, which are line level.

While the input signal to an sound power amplifier, such as the signal from an electrical guitar, may measure merely a few hundred microwatts, its output may exist a few watts for small consumer electronics devices, such as clock radios, tens or hundreds of watts for a home stereo system, several thousand watts for a nightclub'due south sound system or tens of thousands of watts for a large rock concert sound reinforcement organisation. While power amplifiers are available in standalone units, typically aimed at the howdy-fi audiophile marketplace (a niche marketplace) of audio enthusiasts and sound reinforcement system professionals, most consumer electronics sound products, such as clock radios, boomboxes and televisions have relatively small ability amplifiers that are integrated into the production.

History [edit]

De Forest's prototype audio amplifier of 1914.

The audio amplifier was invented effectually 1912 by Lee de Forest, fabricated possible by his invention of the starting time practical amplifying electrical component, the triode vacuum tube (or "valve" in British English language) in 1907. The triode was a three terminal device with a control filigree that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the offset AM radio.^[2] Early audio power amplifiers were based on vacuum tubes and some of these accomplished notably high sound quality (eastward.1000., the Williamson amplifier of 1947–ix).

Audio power amplifiers based on transistors became applied with the wide availability of cheap transistors in the late 1960s. Since the 1970s, most modern sound amplifiers are based on solid-state transistors, especially the bipolar junction transistor (BJT) and the metal–oxide–semiconductor field-consequence transistor (MOSFET). Transistor-based amplifiers are lighter in weight, more than reliable and require less maintenance than tube amplifiers.

The MOSFET, invented by Mohamed Atalla and Dawon Kahng at Bong Labs in 1959,^[3] was adjusted into a power MOSFET for audio by Jun-ichi Nishizawa at Tohoku University in 1974.^[4] Power MOSFETs were soon manufactured by Yamaha for their how-do-you-do-fi audio amplifiers. JVC, Pioneer Corporation, Sony and Toshiba also began manufacturing amplifiers with power MOSFETs in 1974.^[4] In 1977, Hitachi introduced the LDMOS (lateral diffused MOS), a type of power MOSFET. Hitachi was the merely LDMOS manufacturer between 1977 and 1983, during which time LDMOS was used in audio power amplifiers from manufacturers such as HH Electronics (V-series) and Ashly Audio, and were used for music and public address systems.^[4] Class-D amplifiers became successful in the mid-1980s when low-cost, fast-switching MOSFETs were made bachelor.^[five] Many transistor amps utilize MOSFET devices in their power sections, because their distortion curve is more tube-like.^[6]

In the 2010s, there are even so audio enthusiasts, musicians (peculiarly electric guitarists, electric bassists, Hammond organ players and Fender Rhodes electric pianoforte players, amongst others), audio engineers and music producers who prefer tube-based amplifiers, and what is perceived as a "warmer" tube sound.

Blueprint parameters [edit]

Key design parameters for audio power amplifiers are frequency response, proceeds, racket, and distortion. These are interdependent; increasing proceeds often leads to undesirable increases in noise and baloney. While negative feedback actually reduces the gain, it also reduces distortion. Most audio amplifiers are linear amplifiers operating in class AB.

Until the 1970s, most amplifiers used vacuum tubes. During the 1970s, tube amps were increasingly replaced with transistor-based amplifiers, which were lighter in weight, more than reliable, and lower maintenance. Even so, tube preamplifiers are nevertheless sold in niche markets, such every bit with dwelling hi-fi enthusiasts, audio engineers and music producers (who employ tube preamplifiers in studio recordings to "warm upwardly" microphone signals) and electric guitarists, electric bassists and Hammond organ players, of whom a minority proceed to apply tube preamps, tube ability amps and tube effects units. While hi-fi enthusiasts and sound engineers doing live sound or monitoring tracks in the studio typically seek out amplifiers with the lowest distortion, electric instrument players in genres such as dejection, rock music and heavy metal music, among others, employ tube amplifiers because they similar the natural overdrive that tube amps produce when pushed difficult.

The Course-D amplifier, which is much more efficient than Course AB amplifiers, is now widely used in consumer electronics audio products, bass amplifiers and sound reinforcement arrangement gear, equally Class D amplifiers are much lighter in weight and produce much less heat.

Filters and preamplifiers [edit]

Since mod digital devices, including CD and DVD players, radio receivers and tape decks already provide a "flat" signal at line level, the preamp is not needed other than as a book control and source selector. Ane alternative to a separate preamp is to only utilize passive volume and switching controls, sometimes integrated into a ability amplifier to form an integrated amplifier.

Power output stages [edit]

The last stage of amplification, after preamplifiers, is the output stage, where the highest demands are placed on the transistors or tubes. For this reason, the design choices made around the output device (for single-ended output stages, such as in single-concluded triode amplifiers) or devices (for push button-pull output stages), such as the Class of performance of the output devices is oft taken as the description of the whole power amplifier. For example, a Class B amplifier will probably have merely the high power output devices operating cutting off for half of each cycle, while the other devices (such as differential amplifier, voltage amplifier and possibly even driver transistors) operate in Form A. In a transformerless output stage, the devices are essentially in series with the ability supply and output load (such as a loudspeaker), possibly via some big capacitor and/or small-scale resistances.

Further developments [edit]

For some years following the introduction of solid state amplifiers, their perceived sound did non accept the first-class audio quality of the all-time valve amplifiers (meet valve audio amplifier). This led audiophiles to believe that "tube sound" or valve sound had an intrinsic quality due to the vacuum tube engineering itself. In 1970, Matti Otala published a newspaper on the origin of a previously unobserved form of distortion: transient intermodulation distortion (TIM),^[7] later also called slew-induced distortion (SID) by others.^[viii] TIM distortion was found to occur during very rapid increases in amplifier output voltage.^[ix]

TIM did non appear at steady state sine tone measurements, helping to hide it from pattern engineers prior to 1970. Problems with TIM distortion stem from reduced open loop frequency response of solid country amplifiers. Further works of Otala and other authors found the solution for TIM baloney, including increasing slew rate, decreasing preamp frequency bandwidth, and the insertion of a lag compensation circuit in the input stage of the amplifier.^[x] ^[xi] ^[12] In high quality mod amplifiers the open loop response is at least 20 kHz, canceling TIM distortion.

The next step in advanced design was the Baxandall Theorem, created by Peter Baxandall in England.^[13] This theorem introduced the concept of comparing the ratio between the input distortion and the output distortion of an amplifier. This new idea helped audio design engineers to meliorate evaluate the distortion processes within an amplifier.

Applications [edit]

Pyle two-aqueduct power amplifier

Important applications include public accost systems, theatrical and concert sound reinforcement systems, and domestic systems such every bit a stereo or home-theatre organisation. Instrument amplifiers including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers. In some cases, the power amplifier for an instrument amplifier is integrated into a single amplifier "head" which contains a preamplifier, tone controls, and electronic effects. These components may be mounted in a wooden speaker chiffonier to create a "combo amplifier". Musicians with unique performance needs and/or a demand for very powerful amplification may create a custom setup with separate rackmount preamplifiers, equalizers, and a ability amplifier mounted in a 19" road instance.

Power amplifiers are available in standalone units, which are used by hi-fi audio enthusiasts and designers of public address systems (PA systems) and sound reinforcement systems. A hullo-fi user of power amplifiers may have a stereo power amplifier to drive left and right speakers and a single-channel (mono) power amplifier to drive a subwoofer. The number of power amplifiers used in a sound reinforcement setting depends on the size of the venue. A small coffeehouse may have a single ability amp driving two PA speakers. A nightclub may accept several power amps for the primary speakers, i or more than power amps for the monitor speakers (pointing towards the ring) and an additional power amp for the subwoofer. A stadium concert may accept a large number of power amps mounted in racks. Most consumer electronics audio products, such every bit TVs, blast boxes, abode cinema sound systems, Casio and Yamaha electronic keyboards, "combo" guitar amps and car stereos take ability amplifiers integrated inside the chassis of the chief product.

References [edit]

^ "1 – Integrated Amplifier (All Versions)". Archived from the original on 2011-04-24. Retrieved 2011-01-16 . Cyrus Sound: Product Archive: Cyrus One
^ The Transistor in a Century of Electronics. nobelprize.org
^ "Rethink Power Density with GaN". Electronic Design. 21 April 2017. Retrieved 23 July 2019.
^ ^a ^b ^c Duncan, Ben (1996). Loftier Operation Sound Power Amplifiers. Elsevier. pp. 177–8, 406. ISBN9780080508047.
^ Duncan, Ben (1996). Loftier Functioning Sound Power Amplifiers. Newnes. pp. 147–148. ISBN9780750626293.
^ Fliegler, Ritchie; Eiche, Jon F. (1993). Amps! The Other Half of Rock 'n' Roll. Hal Leonard Corporation. ISBN9780793524112.
^ Otala, M. (1970). "Transient distortion in transistorized sound power amplifiers". IEEE Transactions on Audio and Electroacoustics. xviii (3): 234–239. doi:10.1109/TAU.1970.1162117. S2CID 13952562.
^ Jung, Walter Yard.; Stephens, Mark L. and Todd, Craig C. (June 1979). "An overview of SID and TIM". Sound. {{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Otala, Matti (June 1972). "Circuit Design Modifications for Minimizing Transient Intermodulation Distortion in Audio Amplifiers". Journal of the Audio Technology Social club. 20 (v).
^ Lammasniemi, Jorma; Nieminen, Kari (May 1980). "Distribution of the Phonograph Indicate Rate of Change". Journal of the Audio Engineering Society. 28 (v). {{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Petri-Larmi, M.; Otala, Chiliad.; Lammasniemi, J. (March 1980). "Psychoacoustic Detection Threshold of Transient Intermodulation Baloney". Periodical of the Audio Technology Order. 28 (three).
^ Give-and-take of practical design features that can provoke or lessen slew-rate limiting and transient intermodulation in audio amplifiers tin besides be found for example in Hood, John Linsley (1993). "Ch. nine". The Fine art of Linear Electronics. Oxford: Butterworth-Heinemann. doi:10.1016/B978-0-7506-0868-eight.50013-8. ISBN978-0-7506-0868-8.
^ Baxandall, Peter (February 1979) "Audio power amplifier design", Wireless World magazine