Instruct: Given a question, retrieve documents that answer the question.
Query: When was the first power amplifier created?
The development of thermionic valves starting around 1902, provided an entirely electronic method of amplifying signals. The first practical version of such devices was the Audion triode, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Since the only previous device which was widely used to strengthen a signal was the relay used in telegraph systems, the amplifying vacuum tube was first called an "electron relay". The terms "amplifier" and "amplification", derived from the Latin "amplificare", ("to enlarge or expand"), were first used for this new capability around 1915 when triodes became widespread.
The Fender Tremolux was a guitar amplifier made by Fender. It was introduced in the summer of 1955 with a rated power output of 15 watts, cathode bias, two 6V6 output tubes, and a 5V4 tube rectifier. The Tremolux was the first Fender amp with a built in effect, tremolo.
De Forest's Audion did not see much use until its ability to amplify was recognized around 1912 by several researchers, who used it to build the first successful amplifying radio receivers and electronic oscillators. The many uses for amplification motivated its rapid development. By 1913 improved versions with higher vacuum were developed by Harold Arnold at American Telephone and Telegraph Company, which had purchased the rights to the Audion from De Forest, and Irving Langmuir at General Electric, who named his tube the "Pliotron", These were the first vacuum tube triodes. The name "triode" appeared later, when it became necessary to distinguish it from other kinds of vacuum tubes with more or fewer elements (e.g. diodes, tetrodes, pentodes, etc.). There were lengthy lawsuits between De Forest and von Lieben, and De Forest and the Marconi Company, who represented John Ambrose Fleming, the inventor of the diode.
The development of transistors in 1948 by Bell Laboratories led to major improvements to the hearing aid. The transistor was invented by John Bardeen, Walter Brattain, and William Shockley. Transistors were created to replace vacuum tubes; they were small, required less battery power and had less distortion and heat than their predecessor. These vacuum tubes were typically hot and fragile, so the transistor was the ideal replacement.The 1952 Sonotone 1010 used a transistor stage along with vacuum tubes, to extend battery life. The size of these transistors led to developments in miniature, carbon microphones. These microphones could be mounted on various items, even eyeglasses. In 1951, Raytheon manufactured the transistor and was one of the first companies to mass-produce transistors to throughout America. Raytheon realized that their hearing aid only lasted short-term and began to sell the vacuum-tube hearing aids again along with transistor hearing aids.
The first person to use resonant circuits in a radio application was Nikola Tesla, who invented the resonant transformer in 1891. At a March 1893 St. Louis lecture he had demonstrated a wireless system that, although it was intended for wireless power transmission, had many of the elements of later radio communication systems. A grounded capacitance-loaded spark-excited resonant transformer (his "Tesla coil") attached to an elevated wire monopole antenna transmitted radio waves, which were received across the room by a similar wire antenna attached to a receiver consisting of a second grounded resonant transformer tuned to the transmitter's frequency, which lighted a Geissler tube. This system, patented by Tesla 2 September 1897, 4 months after Lodge's "syntonic" patent, was in effect an inductively coupled radio transmitter and receiver, the first use of the "four circuit" system claimed by Marconi in his 1900 patent "(below)". However, Tesla was mainly interested in wireless power and never developed a practical radio "communication" system.
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
Electric sound recording and reproduction are electrical or mechanical techniques and devices for the inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. Acoustic analog recording is achieved by a small microphone diaphragm that can record sound waves on a phonograph (in which a stylus senses grooves on a record) or magnetic tape. The first practical sound recording and reproduction device was the mechanical phonograph cylinder, invented by Thomas Edison in 1877 and patented in 1878. 
The next major technical development was the invention of the gramophone disc in 1889. For much of the 20th century, records were the most common way of selling sound recordings. The widespread availability of records and the development of radio broadcasting enabled a much larger proportion of people to listen to songs and pieces performed by the top artists, enabling the development of national and even international musical stars. In the 1970s, the compact cassette became a major consumer audio format. Advances in electronic and mechanical miniaturization led to the development of the Sony Walkman, a pocket-sized cassette player introduced in 1979, which allowed consumers to listen to their favourite albums outside of their home.
In the early 1920s, Drs. Walter H. Schottky and Erwin Gerlach co-invented the first ribbon microphone. By turning the ribbon circuit in the opposite direction, they also invented the first ribbon loudspeaker. A few years later, Dr. Harry F. Olson of RCA started developing ribbon microphones using field coils and permanent magnets. The RCA Photophone Type PB-31 was commercially manufactured in 1931, greatly impacting the audio recording and broadcasting industries. Condenser microphones at the time could not compare to its frequency response. Radio City Music Hall employed PB-31s in 1932. The following year, the 44A came on the scene. Its tone and pattern control helped reduce reverberation. Many RCA ribbon models are still in use and valued by audio engineers.
The first widely used solid-state negative resistance device was the tunnel diode, invented in 1957 by Japanese physicist Leo Esaki. Because they have lower parasitic capacitance than vacuum tubes due to their small junction size, diodes can function at higher frequencies, and tunnel diode oscillators proved able to produce power at microwave frequencies, above the range of ordinary vacuum tube oscillators. Its invention set off a search for other negative resistance semiconductor devices for use as microwave oscillators, resulting in the discovery of the IMPATT diode, Gunn diode, TRAPATT diode, and others. In 1969 Kurokawa derived conditions for stability in negative resistance circuits. Currently negative differential resistance diode oscillators are the most widely used sources of microwave energy, and many new negative resistance devices have been discovered in recent decades.
From November 17, 1947, to December 23, 1947, John Bardeen and Walter Brattain at AT&T's Bell Labs in Murray Hill, New Jersey of the United States performed experiments and observed that when two gold point contacts were applied to a crystal of germanium, a signal was produced with the output power greater than the input. Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors. The term "transistor" was coined by John R. Pierce as a contraction of the term "transresistance". According to Lillian Hoddeson and Vicki Daitch, authors of a biography of John Bardeen, Shockley had proposed that Bell Labs' first patent for a transistor should be based on the field-effect and that he be named as the inventor. Having unearthed Lilienfeld’s patents that went into obscurity years earlier, lawyers at Bell Labs advised against Shockley's proposal because the idea of a field-effect transistor that used an electric field as a "grid" was not new. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the first point-contact transistor. In acknowledgement of this accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the 1956 Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect".
About 20 years later, John Ambrose Fleming (scientific adviser to the Marconi Company
and former Edison employee) realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in Britain on November 16, 1904 (followed by in November 1905).
Philco had developed and produced a miniature transistorized computer brain for the Navy's jet fighter planes in 1955, which was called the "Transac" (C-1000, C-1100) and which stood for "Transistor Automatic Computer". It used Philco's high-frequency surface-barriers transistors in its circuitry design.
Chrysler and Philco announced that they had developed and produced the world's first all-transistor car radio and it was announced in the April 28, 1955, edition of the "Wall Street Journal". Chrysler made the all-transistor car radio, Mopar model 914HR, available in Fall 1955 for its new line of 1956 Chrysler and Imperial cars, as a $150 option. Philco's radio manufacturing plant in Sandusky, Ohio, had produced the all-transistor car radio unit for the Chrysler Corporation, which also used Philco's surface-barrier transistors in its circuitry design.
In 1955, Philco developed and produced the world's first all-transistor phonograph models TPA-1 and TPA-2. This was originally announced in the June 28, 1955, edition of the "Wall Street Journal". Philco had begun selling these all-transistor phonographs in the fall of 1955 for $59.95. The October 1955 issue of "Radio & Television News" magazine (page 41) printed a full-page, detailed article, on Philco's new consumer product all-transistor phonograph. The Philco all-transistor portable phonograph TPA-1 and TPA-2 models played only 45rpm records and used four 1.5v "D" batteries for its power supply. "TPA" stands for "Transistor Phonograph Amplifier". Its circuitry used three Philco germanium PNP alloy-fused junction audio frequency transistors. After the 1956 season ended, Philco decided to discontinue the all-transistor portable 45rpm phonograph models, for transistors were too expensive compared to vacuum tubes.
The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Julius Edgar Lilienfeld patented a field-effect transistor in 1926 but it was not possible to actually construct a working device at that time. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley. The transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and Bardeen, Brattain, and Shockley shared the 1956 Nobel Prize in Physics for their achievement.
During 1958, Fender introduced the model 5F6-A Bassman model. This final 1950s Tweed Bassman model product line included a change from the 5Y3 to the GZ34 rectifier tube, as well as a modification within the Presence control circuit. During early 1960, Fender began producing the 5F6-A Bassman with Jensen P10Q speakers. The P10Q Jensen speakers are more able to manage stronger electrical input power and generate better "clean" output sounds than previous installed P10R Jensen speakers. The P10R Jensen speakers were shipped within all Fender Bassmen from late 1954 until early 1960. Many professional music industry analysts have heralded the 1950s Fender 4×10 Bassman amps as the greatest guitar amp ever. The first 1954 Fender Tweed 5D6 4×10 circuit generated further Tweed Bassman amplifier development through 1960. Several Bassman models were progressively influenced by the 5D6 through the last Fender Tweed 5F6-A Bassman's circuit design. The 5F6-A Bassman's design was directly copied by Marshall Amplifiers within their JTM-45 amplifier during the early 1960s.
One of the first solid-body guitars was invented by Les Paul. Gibson did not present their Gibson Les Paul guitar prototypes to the public, as they did not believe the solid-body style would catch on. Another early solid-body Spanish style guitar, resembling what would become Gibson's Les Paul guitar a decade later, was developed in 1941 by O.W. Appleton, of Nogales, Arizona. Appleton made contact with both Gibson and Fender but was unable to sell the idea behind his "App" guitar to either company. In 1946, Merle Travis commissioned steel guitar builder Paul Bigsby to build him a solid-body Spanish-style electric. Bigsby delivered the guitar in 1948. The first mass-produced solid-body guitar was Fender Esquire and Fender Broadcaster (later to become the Fender Telecaster), first made in 1948, five years after Les Paul made his prototype. The Gibson Les Paul appeared soon after to compete with the Broadcaster. Another notable solid-body design is the Fender Stratocaster, which was introduced in 1954 and became extremely popular among musicians in the 1960s and 1970s for its wide tonal capabilities and more comfortable ergonomics than other models.
The first AC commutator-free three-phase induction motors were independently invented by Galileo Ferraris and Nikola Tesla, a working motor model having been demonstrated by the former in 1885 and by the latter in 1887. Tesla applied for US patents in October and November 1887 and was granted some of these patents in May 1888. In April 1888, the "Royal Academy of Science of Turin" published Ferraris's research on his AC polyphase motor detailing the foundations of motor operation. In May 1888 Tesla presented the technical paper "A New System for Alternating Current Motors and Transformers" to the "American Institute of Electrical Engineers" (AIEE)
Thomas A. Edison invented the phonograph, the first device for recording and playing back sound, in 1877. After patenting the invention and benefiting from the publicity and acclaim it received, Edison and his laboratory turned their attention to the commercial development of electric lighting, playing no further role in the development of the phonograph for nearly a decade. Edison's original phonograph recorded on sheets of tinfoil and was little more than a crude curiosity, although one that fascinated much of the public. These earliest phonographs were sold mainly to entrepreneurs who made a living out of traveling around the country giving "educational" lectures in hired halls or otherwise demonstrating the device to audiences for a fee. The tinfoil phonograph was not fit for any real practical use and public interest soon waned.
The development of the cavity magnetron in the UK made possible the production of electromagnetic waves of a small enough wavelength (microwaves). American engineer Percy Spencer is generally credited with inventing the modern microwave oven after World War II from radar technology developed during the war. Named the "Radarange", it was first sold in 1946. Raytheon later licensed its patents for a home-use microwave oven that was first introduced by Tappan in 1955, but these units were still too large and expensive for general home use. Sharp Corporation introduced the first microwave oven with a turntable between 1964 and 1966. The countertop microwave oven was first introduced in 1967 by the Amana Corporation. After Sharp introduced low-cost microwave ovens affordable for residential use in the late 1970s, their use spread into commercial and residential kitchens around the world. In addition to their use in cooking food, types of microwave ovens are used for heating in many industrial processes.
In 1959, Harman Kardon marketed the Citation II, an early ultra wideband stereophonic tube amplifier. Designed by Stewart Hegeman, it featured 60 watts/channel output with a frequency response of 18-60,000 Hz at 20 watt output. The company promoted their philosophy of designing high fidelity sound using amplifiers that provided widest possible audio bandwidth. Although the human ear highest audible range is around 20,000 Hz, the full range of sound goes beyond that with harmonics and overtones that may be beyond the hearing range of the human ear. These harmonics interact with other frequencies to produce audible secondary sounds or interference. Harman Kardon promoted the design in audio magazines and product brochures.
While at the Westinghouse subsidiary in Paris, Welker and German physicist Herbert F. Mataré developed a point contact semiconductor amplifier, demonstrated in June 1948. This coincided with the announcement by Bell laboratory scientists of the demonstration of a point contact transistor on June 30, 1948. The French Westinghouse subsidiary applied for a patent on the same type of device on August 13, 1948. On 18 May 1949, this European invention coined as the "Le Transistron" or the "French transistor" was presented to the public, while a first batch of 1,000 devices was manufactured for the French telecommunications. This development was an outgrowth of work done by the two independently in Germany in programs to develop German radar. The French patent was granted in 1952.
German inventor Johann Philipp Reis designed an early sound transmitter that used a metallic strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the "liquid transmitter" design in Scottish-American Alexander Graham Bell's telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a very poor sound quality.
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone. This was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent (after a long legal dispute) in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention. The carbon microphone is the direct prototype of today's microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886. This microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910.
In 1916, E.C. Wente of Western Electric developed the next breakthrough with the first condenser microphone. In 1923, the first practical moving coil microphone was built. The Marconi-Sykes magnetophone, developed by Captain H. J. Round, became the standard for BBC studios in London. This was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day.
The company was founded in the late 1970s by Jean-Pierre (John) Prideaux to build power amplifiers for the tour sound industry. The first amplifier, the P3500, delivered 475 watts-per-channel in a chassis that occupied a two-rack space at a time when competitors were offering 400 watts in a four-rack space. In 1983, the 4001 amplifier was the first to provide two-ohms in a three-rack space chassis. Four years later the 8001 power amplifier became an industry standard concert sound amplifier. It was superseded by the 8002 model in 1998.
In 1965, Pete Townshend and John Entwistle were directly responsible for the creation and widespread use of Marshall amplifiers powering stacked speaker cabinets. In fact, the first 100 watt Marshall amps (called "Superleads") were created specifically for Entwistle and Townshend when they wanted an amplifier that sounded like a Fender head but with much more power.
Electrocompaniet was established in 1973 by Per Abrahamsen and Svein Erik Børja. Their idea was to create a Transistor amplifier that did not sound as bad as the transistor amplifiers did at the time. They based the circuits on research done by Finnish Dr. Matti Otala of Tampere University of Technology. The finished product was a 25 Watt power amplifier named 
"The 2 Channel Audio Power Amplifier", It was also called "The Otala Amplifier". They continued development on the product. And in 1976 The worlds biggest Hifi Magazine at the time ¨The Audio Critic magazine¨ reviewed the amplifier and wrote: 
“Audio freaks – eat your hearts out. This is the world’s best sounding amplifier.” And in 1991
Michael Jackson's producer Bruce Swedien was contacted by Nils Bjarne Kvam one of the biggest producers in Norway at the time, and he told him about the amplifiers of Electrocompaniet, and Swedien started getting interested. The amplifier was packed and shipped to the US in September 1991. Bruce was busy at the time since he was working with the last mix to Jackson's "Dangerous". He LOVED the amplifiers, and wanted to use it on the album, but the album was almost done, and he would then have to remaster it all over again since the difference was so big. Swedien was ready to use the amplifiers on the next albums. He used it for the first time with Sergio Mendez, and when he walked in the recording studio with Jackson in January 1995 he really started using them. The next two albums "" and "Invincible" was mastered with the amplifiers, and both albums thanked Electrocompaniet with '`Special thanks to Electrocompaniet¨ with logo on its covers.
During the same era (late 1970s) PS Audio introduced its first power amplifier, the Model One, a solid state design producing 70 watts per channel into 8 Ohms and 140 watts per channel into 4 Ohms. The design was a classic AB amplifier design featuring the company's first full 19" chassis design, large power supply, low feedback and minimalist design constraints. The Model One was later followed with the world's first Audiophile integrated amplifier introduced by an American High-End company, the Elite. Based on the Model One architecture, the Elite integrated the Linear Control Center into a Model One amplifier chassis. The Model One was replaced by the Model II, moving back to a smaller modular chassis approach at 8.5" with faceplate. The Model II produced 40 watts per channel into 8 Ohms, 70 watts per channel into 4 Ohms and had a Bridging switch enabling the user to bridge the internal stereo amplifiers into one mono amplifier, producing 160 watts into 4 Ohms. The Model II was followed by the IIC, featuring the same circuitry placed into a standard 19" rack mount chassis. The IIC introduced a new concept to the Audiophile marketplace, use of a separate external power supply for an amplifier. Users could choose from two models of external power supply, one as standard and an upgrade to a larger High Current version. The concept of an external power supply was first introduced on the PS Audio IV preamplifier and later applied to power amplifiers like the IIC. The concept became known as the High Current Power Supply or HCPS and was popular because improvements to the sound quality were gained by moving to a larger power supply, both in the application of the preamplifier as well as power amplifiers. The model IIC is factory rated at 55 watts into 8 ohms and 200 watts bridged mode (400 watts into 4 ohms bridged). The IIC Plus is rated at 70 watts into 8 ohms. Amplifier successors to the IIC included the 250 Delta monoblock and the 100 Delta amplifier.