 Type A, c. 1945 | |
| Uses | Broadcasting, Sound recording |
|---|---|
| Inventor | F W Alexander |
| Manufacturer | BBC/Marconi |
| Model | A, AX, AXB, AXBT |
The BBC-Marconi Type A [1] is a ribbon microphone that was produced by the BBC [2] and Marconi between 1934 and 1959. [3] The microphone has been described as "iconic" [4] and a symbol of the BBC. [5]
In the early 1930s, the BBC became aware of RCA's model 44 ribbon microphone that was used in Hollywood. [1] [6] Each pair of microphone and amplifier would have cost the BBC £130 (approximately £6,500 in 2009. because of inflation) [6] [7] ). As this was not within the BBC's budget, they designed their own microphone, the Type A, alongside Marconi. There were initial concerns that the new design infringed the patent of the RCA microphone, but these were overcome. [6] The Type A was produced at a cost of £9 each (approximately £475 in 2009). [6] [7]
The original Type A microphone was designed by engineer F. W. Alexander [8] under the guidance of H. L. Kirke's Research Department at the BBC. [9]
In 1940, the Type A was used in the broadcast of Charles de Gaulle's 1940 appeals. [4]
In the early 1950s, the BBC began to design the Type A's successor. The first model was the pressure gradient PGD design. [4] In 1953, production began on the PGS (pressure gradient single) ribbon microphone in agreement with the company Standard Telephones and Cables (STC). In the mid-1970s, STC's manufacturing was transferred to Coles Electroacoustics, [10] who continue to manufacture the PGS under the model number 4038. [4] [9] [11]
Four versions of the microphone were produced – the "A", "AX", "AXB", and "AXBT". [2] The original microphone used a thick aluminium ribbon which produced a harsh resonance. [1] This was soon replaced with a thinner ribbon, and was named Type AX. [1] In 1943, the AXB model was launched, which featured balanced wiring. [12] In 1944, the microphone was renamed the AXBT with the addition of a Ticonal magnet to increase sensitivity by 6 decibels. [1] [12] The AXBT weighed approximately 9.25 pounds (4.20 kg). [6]
The microphone had a figure-of-eight polar pattern. [2] The aluminium ribbon was less than one micrometre thick. [3]
Sir John Ambrose Fleming FRS was an English electrical engineer and physicist who invented the first thermionic valve or vacuum tube, designed the radio transmitter with which the first transatlantic radio transmission was made, and also established the right-hand rule used in physics.
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A microphone, colloquially called a mic, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers for recording voice, speech recognition, VoIP, and for other purposes such as ultrasonic sensors or knock sensors.
Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighbouring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander Graham Bell.
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Sir William Henry Preece was a Welsh electrical engineer and inventor. Preece relied on experiments and physical reasoning in his life's work. Upon his retirement from the Post Office in 1899, Preece was made a Knight Commander of the Order of the Bath (KCB) in the 1899 Birthday Honours.
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A ribbon microphone, also known as a ribbon velocity microphone, is a type of microphone that uses a thin aluminum, duraluminum or nanofilm of electrically conductive ribbon placed between the poles of a magnet to produce a voltage by electromagnetic induction. Ribbon microphones are typically bidirectional, meaning that they pick up sounds equally well from either side of the microphone.
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The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granules of carbon. One plate is very thin and faces toward the speaking person, acting as a diaphragm. Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in a modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In telephony, this undulating current is directly passed through the telephone wires to the central office. In public address systems it is amplified by an audio amplifier. The frequency response of most carbon microphones, however, is limited to a narrow range, and the device produces significant electrical noise.
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