1.
Production sound mixer
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This requires choice and deployment of microphones, choice of recording media, and mixing of audio signals in real time. The recordist may be asked to capture a variety of wild sound on location. The recorded production sound track is later combined with elements, i. e. effects, music, narration. The Practical Art of Motion Picture Sound, vincent Magnier, Le guide de la prise de son pour limage. John Purcell, Dialogue Editing for Motion Pictures, A Guide to the Invisible Art, ISBN0240809181 Jay Rose, Producing Great Sound for Film and Video. Focal Press, fourth edition 2014 Book info, make Your Movie Sound Like A Real Movie Martinez, Carlos E. Location Audio for Any Budget, An Introduction Rose, Jay Film/video tutorials written for DV Magazine and others
2.
Live sound mixing
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Live sound mixing is the process of electrically or digitally blending together multiple sound sources at a live event by an audio engineer using a mixing console. Sounds that are mixed include those from instruments and voices which are picked up by microphones and pre-recorded material, individual sources are typically equalised to adjust the bass and treble response and routed to effect processors to ultimately be amplified and reproduced via a loudspeaker system. The live sound engineer balances the various sources in a way that best suits the needs of the event. Audio equipment is connected together in a sequence known as the signal chain. In live sound situations, this consists of input transducers like microphones, pickups and these devices are connected, often via multicore cable, to individual channels of a mixing console that allows these inputs to be modified in various ways before they are electrically summed. Audio signal processing may be applied to individual inputs, groups of inputs, or the output mix. The front of house engineer focuses on mixing audio for the audience, the output signals from the FOH console connects to a Sound reinforcement system. Other non-audio crew members, such as the console operator, might also work from the FOH position. The foldback or monitor engineer focuses on mixing the sound that the performers hear on stage via a monitor system. The monitor engineers role is important where the instruments and voices on the area is amplified. Usually, individual performers receive personalised feeds either via monitors placed on the floor in front of them or via in-ear monitors. The monitor engineers console is placed in the wings just off-stage. For small events, often a sound check is conducted a few hours before the show, once all the instruments are set up, the engineer asks each instrumentalist to perform alone, so that the levels and equalization for the instruments can be adjusted. Since a drum kit contains a number of drums, cymbals and percussion instruments, once the sound of each individual instrument is set, the engineer asks the band to play a song from their repertoire, so that the levels of one instrument versus another can be adjusted. Mics are set up for the lead vocalist and backup vocalist, the final part of the sound check is to have the rhythm section and all the vocalists perform a song from their repertoire. During this song, the engineer can adjust the balance of the different instruments and vocalists and this allows the sound of the instruments and vocals to be fine-tuned prior to the audience hearing the first song. In the 2010s, many bands and major venues use digital mixing consoles that have automated controls. The settings of previous shows can be saved and recalled in the console, automated mixing consoles are a great time saver for concerts where a main band is preceded by several support acts
3.
Solid State Logic
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Solid State Logic is a manufacturer of high-end mixing consoles and recording studio hardware headquartered in Begbroke, Oxfordshire, United Kingdom. Founded in 1969, SSL has since expanded to its present 15 acre science park in Oxfordshire, the company invents, designs and manufactures technology for the manipulation of sound and the production and delivery of video. SSL employs over 160 people worldwide and has offices in Los Angeles, Milan, New York, Paris. One of the first SSL consoles was a 4000B installed at The Townhouse Studios on Goldhawk Road in London, possibly the earliest 4000E console was at RG Jones in London, closely followed by Eden Studios and Sarm Studios. Eden had a 48-channel console with integral patch and automation using 8 floppy drives, Sarm East had a 40-channel console with remote patchbay and automation with 8 floppy drives. Both consoles had Total Recall enabling console settings to be recalled & remade with a degree of accuracy. SSL analogue and digital audio consoles are used in both pre- and post-production for film, audio, video and broadcast sound. Notably, in May 2001, Studio 3 at Abbey Road Studios was refurbished with a 96-channel SSL9000 J series console, the largest SSL console in Europe. Westlake Recording Studios in West Hollywood, California, which makes extensive use of SSL consoles, was fitted out with an SSL9000 K console in its main studio in 2013. SSL also produces rackmount audio hardware for use in recording studios, in 2005, SSL was purchased by musician Peter Gabriel and broadcast entrepreneur David Engelke. The change of ownership has seen changes in strategy for the company including new product releases to address the fast-changing state of the pro-audio marketplace. There are over 3,000 SSL systems in service around the world and their equipment has been used by classical musicians and popular artists such as Nine Inch Nails, Bryan Adams, Peter Gabriel, Whitney Houston, Blur, Jean-Michel Jarre and Sting. Rede Record, Brasil The 1970s recording scene was dominated by large format consoles feeding multi-track tape machines manufactured by such as Studer. Both the equipment and the environment they were used in were expensive to source, a series of developments have slowly eroded this position. Perhaps the first major change was the advent of music sequencer technology, prior to its introduction all synchronisation was achieved by adding SMPTE time code to analogue tape. This acted as a point so that individual tracks could be easily synchronised. With the advent of MIDI hardware, devices could be used to synchronise any MIDI device, continuing development in this area has led to computer-controlled sequencing. The development of converter technology transforming analogue signals into digital signals has spawned a variety of supporting technical developments, DSP or Digital Signal Processing technology has led both to the advent of digital mixing desks and DSP-based computer recording platforms such as Pro Tools
4.
Sound recording and reproduction
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Sound recording and reproduction is an electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording, prior to the development of analog recording, there were mechanical systems for reproducing instrumental music, such as wind-up music boxes and later, in the late 19th century, player pianos. Analog sound reproduction is the process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Digital recording and reproduction converts the sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a variety of media. Whereas successive copies of an analog recording tend to degrade in quality, as noise is added. A digital audio signal must be reconverted to analog form during playback before it is amplified and connected to a loudspeaker to produce sound, long before sound was first recorded on cylinders or records, music was recorded—first by written music notation, then also by mechanical devices. Fowler, this. cylinder with raised pins on the surface remained the device to produce and reproduce music mechanically until the second half of the nineteenth century. The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine, according to Fowler, the automata were a robot band that performed. more than fifty facial and body actions during each musical selection. In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder, similar designs appeared in barrel organs, musical clocks, barrel pianos, and musical boxes. A music box is a musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth of a steel comb. They were developed from musical snuff boxes of the 18th century, some of the more complex boxes also have a tiny drum and/or bells, in addition to the metal comb. The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books, the player piano, first demonstrated in 1876, used a punched paper scroll that could store an long piece of music. The most sophisticated of the rolls were hand-played, meaning that the roll represented the actual performance of an individual. This technology to record a live performance onto a piano roll was not developed until 1904, piano rolls were in continuous mass production from 1896 to 2008. A1908 U. S. Supreme Court copyright case noted that, in 1902 alone, the use of piano rolls began to decline in the 1920s although one type is still being made today. The first device that could record actual sounds as they passed through the air was the phonautograph, the earliest known recordings of the human voice are phonautograph recordings, called phonautograms, made in 1857. They consist of sheets of paper with sound-wave-modulated white lines created by a stylus that cut through a coating of soot as the paper was passed under it
5.
Sound reinforcement system
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In both cases, these systems reinforce sound to make it louder or distribute it to a wider audience. Some audio engineers and others in the audio industry disagree over whether these audio systems should be called sound reinforcement systems or PA systems. Distinguishing between the two terms by technology and capability is common, while others distinguish by intended use, in some regions or markets, the distinction between the two terms is important, though the terms are considered interchangeable in many professional circles. These primary parts involve varying amounts of components to achieve the desired goal of reinforcing and clarifying the sound to the audience, performers. These signal inputs are plugged into the input jacks of a thick multicore cable, the snake then routes the signals of all of the inputs to either one or two mixing consoles. In these cases, at least two audio engineers are required, one to do the FOH Main mix and one to do the Monitor mix, once the signal arrives at a channel on the mixing console, this signal can be adjusted in many ways by the sound engineer. A signal can be equalized, compressed, or panned before being routed to an output bus. The signal may also be routed into an effects processor, such as a reverb effect, which outputs a wet version of the signal. Many electronic effects units are used in sound reinforcement systems, including digital delay, some concerts use pitch correction effects, which electronically correct any out-of-tune singing. A group of signals may be routed through a bus before being sent to the main bus to allow the engineer to control the levels of several related signals at once. A bus can often be processed just like an input channel. The mix of all the different signals and channels to the master faders on the console. Mixing consoles also have additional sends, also referred to as auxes or aux sends, on each channel so that a different mix can be created. One usage for aux sends is to create a mix of the vocal, another use of an aux send is to select varying amounts of certain channels, and then route these signals to an effects processor. A common example of the use of aux sends is to send all of the vocal signals from a rock band through a reverb effect. While reverb is usually added to vocals in the mix, it is not usually added to electric bass. The next step in the path generally depends on the size of the system in place. In smaller systems, the outputs are often sent to an additional equalizer, or directly to a power amplifier
6.
Electronics
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Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements, the science of electronics is also considered to be a branch of physics and electrical engineering. The ability of electronic devices to act as switches makes digital information processing possible, until 1950 this field was called radio technology because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes. Today, most electronic devices use semiconductor components to perform electron control and this article focuses on engineering aspects of electronics. Components are generally intended to be connected together, usually by being soldered to a circuit board. Components may be packaged singly, or in more complex groups as integrated circuits, some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active or passive, vacuum tubes were among the earliest electronic components. They were almost solely responsible for the revolution of the first half of the Twentieth Century. They took electronics from parlor tricks and gave us radio, television, phonographs, radar, long distance telephony and they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid state devices have all but completely taken over, vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices. The 608 contained more than 3,000 germanium transistors, thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic, circuits and components can be divided into two groups, analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types, most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a range of voltage or current as opposed to discrete levels as in digital circuits. The number of different analog circuits so far devised is huge, especially because a circuit can be defined as anything from a single component, analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, one rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance and this type of circuit is usually called mixed signal rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation, an example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit
7.
Audio mixing (recorded music)
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The track may be mixed in mono, stereo, or surround sound. There are numerous approaches, methods and techniques involved in Audio mixing, some of these practices include levels setting, equalization, stereo panning, Audio mixing techniques and approaches can vary widely, and these can greatly affect the qualities of the sound recording. Audio mixing techniques largely depend on music genres and the quality of sound recordings involved, the process is generally carried out by a mixing engineer, though sometimes the musical producer or music artist may assist. After mixing, a mastering engineer prepares the final product for production, Audio mixing may be transferred onto a mixing console or digital audio workstation. Jay bala ji In the late century, Thomas Edison. The recording and reproduction process itself was completely mechanical with little or no electrical parts, Emile Berliners gramophone system recorded music by inscribing spiraling lateral cuts onto a vinyl disc. Electronic recording became widely used during the 1920s. It was based on the principles of electromagnetic transduction, the possibility for a microphone to be connected remotely to a recording machine meant that microphones could be positioned in more suitable places. Even more useful was the fact that the outputs of the microphones could be mixed before being fed to the disc cutter, before the introduction of multitrack recording, all sounds and effects that were to be part of a record were mixed at one time during a live performance. If the recorded blend wasnt satisfactory, or if one made a mistake. Modern mixing emerged with the introduction of commercial multi-track tape machines, the ability to record sounds into a multitude of channels meant that treating these sounds could be postponed to a later stage– the mixing stage. In the 1980s, home recording and mixing became much easier, the 4-track Portastudio was introduced in 1979. Bruce Springsteen released the album Nebraska in 1982 using one, the Eurythmics topped the charts in 1983 with the song Sweet Dreams, recorded by band member Dave Stewart on a makeshift 8-track recorder. In the mid-to-late 1990s, computers replaced tape-based recording for most home studios, at the same time, digital audio workstations, first used in the mid-1980s, began to replace tape in many professional recording studios. A mixer is the heart of the mixing process. Mixers offer a multitude of inputs, each fed by a track from a multitrack recorder, mixers typically have 2 main outputs or 8. Mixers offer three main functionalities, Mixing – summing signals together, which is normally done by a dedicated summing amplifier or in the case of digital by a simple algorithm, routing – allows the routing of source signals to internal buses or external processing units and effects. Processing – many mixers also offer on-board processors, like equalizers and compressors, Mixing consoles used for dubbing can often be seen as large and intimidating, due to the exceptional amount of controls
8.
Microphone
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A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal. Several different types of microphone are in use, which employ different methods to convert the air pressure variations of a wave to an electrical signal. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced, in order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones, some of the first examples, from fifth century BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheatres. In 1665, the English physicist Robert Hooke was the first to experiment with an other than air with the invention of the lovers telephone made of stretched wire with a cup attached at each end. German inventor Johann Philipp Reis designed an early sound transmitter that used a strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the transmitter design in Scottish-American Alexander Graham Bells telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a poor sound quality. The first microphone that enabled proper voice telephony was the carbon microphone and 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 in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, the carbon microphone is the direct prototype of todays 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 and 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 Skykes or magnetophon, developed by Captain H. J. Round, was the standard for BBC studios in London and this was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the microphone was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson. Over the years these microphones were developed by companies, most notably RCA that made large advancements in pattern control. With television and film technology booming there was demand for high fidelity microphones, electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. During the second half of 20th century development advanced quickly with the Shure Brothers bringing out the SM58, digital was pioneered by Milab in 1999 with the DM-1001. The latest research developments include the use of optics, lasers and interferometers
9.
Digital signal (signal processing)
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If that discrete set is finite, the discrete values can be represented with digital words of a finite width. Most commonly, these values are represented as fixed-point words or floating-point words. The process of analog-to-digital conversion produces a digital signal, common practical digital signals are represented as 8-bit, 16-bit, 24-bit and 32-bit. But the number of levels is not necessarily limited to powers of two
10.
Summation
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In mathematics, summation is the addition of a sequence of numbers, the result is their sum or total. If numbers are added sequentially from left to right, any intermediate result is a sum, prefix sum. The numbers to be summed may be integers, rational numbers, real numbers, besides numbers, other types of values can be added as well, vectors, matrices, polynomials and, in general, elements of any additive group. For finite sequences of elements, summation always produces a well-defined sum. The summation of a sequence of values is called a series. A value of such a series may often be defined by means of a limit, another notion involving limits of finite sums is integration. The summation of the sequence is an expression whose value is the sum of each of the members of the sequence, in the example,1 +2 +4 +2 =9. Addition is also commutative, so permuting the terms of a sequence does not change its sum. There is no notation for the summation of such explicit sequences. If, however, the terms of the sequence are given by a pattern, possibly of variable length. For the summation of the sequence of integers from 1 to 100. In this case, the reader can guess the pattern. However, for more complicated patterns, one needs to be precise about the used to find successive terms. Using this sigma notation the above summation is written as, ∑ i =1100 i, the value of this summation is 5050. It can be found without performing 99 additions, since it can be shown that ∑ i =1 n i = n 2 for all natural numbers n, more generally, formulae exist for many summations of terms following a regular pattern. By contrast, summation as discussed in this article is called definite summation, when it is necessary to clarify that numbers are added with their signs, the term algebraic sum is used. Mathematical notation uses a symbol that compactly represents summation of many terms, the summation symbol, ∑. The i = m under the symbol means that the index i starts out equal to m
11.
Recording studio
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A recording studio is a facility for sound recording and mixing. Ideally both the recording and monitoring spaces are designed by an acoustician or audio engineer to achieve optimum acoustic properties. The engineers and producers listen to the music and the recorded tracks on monitor speakers and/or headphones. Major recording studios typically have a range of large, heavy, Isolation booths are small sound-insulated rooms with doors, designed for instrumentalists. This equipment may interfere with the recording process, Recording studios are carefully designed around the principles of room acoustics to create a set of spaces with the acoustical properties required for recording sound with precision and accuracy. This will consist of both room treatment and soundproofing to prevent sound from leaving the property. Even though sound isolation is a key goal, the musicians, singers, audio engineers and record producers still need to be able to see other, to see cue gestures. As such, the room, isolation booths, vocal booths. Some smaller studios do not have instruments, and bands and artists are expected to bring their own instruments, having musical instruments and equipment in the studio creates additional costs for a studio, as pianos have to be tuned and instruments need to be maintained. However, it makes it convenient for recording artists, as they do not have to bring in large. As well, less costly studio time is spent moving in gear, drummers bring their own snare drum, cymbals and sticks/brushes. The types and brands of equipment owned by a studio depends on the styles of music for the bands. A studio that mainly records heavy metal music will be likely to have large, powerful guitar amp heads, in contrast, a studio which mainly records country bands will likely have a selection of small, vintage combo amps. A studio that records a lot of 1970s-style funk may have an electric piano. General purpose computers have rapidly assumed a role in the recording process. A computer thus outfitted is called a Digital Audio Workstation, or DAW, other software applications include Ableton Live, Mixcraft, Cakewalk Sonar, ACID Pro, FL Studio, Adobe Audition, Auto-Tune, Audacity, and Ardour. While Apple Macintosh is used for most studio work, there is a breadth of available for Microsoft Windows. If no mixing console is used and all mixing is done using only a keyboard and mouse, the OTB is used when mixing with other hardware and not just the PC software
12.
Public address system
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Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. Intercom systems, installed in buildings, have both speakers throughout a building, and microphones in many rooms allowing the occupants to respond to announcements. Sound reinforcement systems and PA systems may use some similar components, Sound reinforcement systems are for live music or performance, whereas PA systems are primarily for reproduction of speech. A short time later the Automatic Enunciator Company was established in Chicago in order to market the new device, in August 1912 a large outdoor installation was made at a water carnival held in Chicago by the Associated Yacht and Power Boat Clubs of America. Seventy-two loudspeakers were strung in pairs at intervals along the docks. The system was used to announce race reports and descriptions, carry a series of speeches about The Chicago Plan, and provide music between races. Four years later, in 1915, they built a dynamic loudspeaker with a 1-inch voice coil, a 3-inch corrugated diaphragm, the electromagnet created a flux field of approximately 11,000 G. Their first experiment used a carbon microphone, when the 12 V battery was connected to the system, they experienced one of the first examples of acoustic feedback. They then placed the loudspeaker on the roof, and claims say that the amplified human voice could be heard 1 mile away. Jensen and Pridham refined the system and connected a phonograph to the loudspeaker to be able to broadcast recorded music and this demonstration was official presentation of the working system, and approximately 100,000 people gathered to hear Christmas music and speeches with absolute distinctness. The first outside broadcast was one week later, again supervised by Jensen. Jensen oversaw the governor using the microphone while Pridham operated the loudspeaker, the following year, Jensen and Pridham applied for a patent for what they called their Sound Magnifying Phonograph. Over the next two years developed their first valve amplifier. In 1919 this was standardized as a 3-stage 25 watt amplifier, wilsons speech was part of his nationwide tour to promote the establishment of the League of Nations. It was held on September 9,1919 at City Stadium, as with the San Francisco installation, Jensen supervised the microphone and Pridham the loudspeakers. Wilson spoke into two large horns mounted on his platform which channelled his voice into the microphone, similar systems were used in the following years by Warren G. Harding and Franklin D. Roosevelt. By the early 1920s, Marconi had established a department dedicated to public address, in 1925, George V used such a system at the British Empire Exhibition, addressing 90,000 via six long-range loudspeakers. This public use of loudspeakers brought attention to the possibilities of such technology, the 1925 Royal Air Force Pageant at Hendon Aerodrome used a Marconi system to allow the announcer to address the crowds, as well as amplify the band
13.
Nightclub
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A nightclub is an entertainment venue and bar which serves alcoholic beverages that usually operates late into the night. Another distinction is that whereas many pubs and sports bars aim at a market, nightclubs typically aim at a niche market of music and dancing enthusiasts. The upmarket nature of nightclubs can be seen in the inclusion of VIP areas in some nightclubs, for celebrities, nightclubs are much more likely than pubs or sports bars to use bouncers to screen prospective clubgoers for entry. Some nightclub bouncers do not admit people with ripped jeans or other clothing or gang apparel as part of a dress code. The busiest nights for a nightclub are Friday and Saturday night, most clubs or club nights cater to certain music genres, such as house music or gothic rock. A nightclub may also be called a discothèque, disco, or dance club, from about 1900 to 1920, working class Americans would gather at honky tonks or juke joints to dance to music played on a piano or a jukebox. Webster Hall is credited as the first modern nightclub, being built in 1886 and starting off as a hall, originally functioning as a home for dance. During Prohibition in the United States, nightclubs went underground as illegal speakeasy bars, with Webster Hall staying open, with rumors circulating of Al Capones involvement and police bribery. With the repeal of Prohibition in February 1933, nightclubs were revived, such as New Yorks 21 Club, Copacabana, El Morocco, in Germany, possibly the first discothèque was Scotch-Club. These discothèques were also patronized by anti-Vichy youth called zazous, there were also underground discothèques in Nazi Germany patronized by anti-Nazi youth called the swing kids. In Harlem, Connies Inn and the Cotton Club were popular venues for white audiences, before 1953 and even some years thereafter, most bars and nightclubs used a jukebox or mostly live bands. The Whisky à Gogo set into place the elements of the modern post World War II discothèque-style nightclub. At the end of the 1950s, several of the bars in Soho introduced afternoon dancing. In the early 1960s, Mark Birley opened a members-only discothèque nightclub, Annabels, in Berkeley Square, in 1962, the Peppermint Lounge in New York City became popular and is the place where go-go dancing originated. However, the first rock and roll generation preferred rough and tumble bars and taverns to nightclubs, disco has its roots in the underground club scene. It brought together people from all walks of life and backgrounds and these clubs acted as safe havens for homosexual partygoers to dance in peace and away from public scrutiny. Disco allowed patrons to explore sexuality and push the envelope on the dance floor, disco clubs acted as an escape from such depressing environments and acted as the fantasy marginalized peoples could escape to forget oppression and racism. Disco clubs originally functioned as liberated party spaces and were seen as places of political statement, a smooth mix of long single records to keep people dancing all night long
14.
Broadcasting
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Broadcasting began with AM radio, which came into popular use around 1920 with the spread of vacuum tube radio transmitters and receivers. Before this, all forms of communication were one-to-one, with the message intended for a single recipient. Over the air broadcasting is usually associated with radio and television, the receiving parties may include the general public or a relatively small subset, the point is that anyone with the appropriate receiving technology and equipment can receive the signal. The field of broadcasting includes both government-managed services such as radio, community radio and public television, and private commercial radio. The U. S. Code of Federal Regulations, title 47, part 97 defines broadcasting as transmissions intended for reception by the general public, private or two-way telecommunications transmissions do not qualify under this definition. For example, amateur and citizens band radio operators are not allowed to broadcast, as defined, transmitting and broadcasting are not the same. Transmissions using a wire or cable, like television, are also considered broadcasts. In the 2000s, transmissions of television and radio programs via streaming digital technology have increasingly been referred to as broadcasting as well, the earliest broadcasting consisted of sending telegraph signals over the airwaves, using Morse code, a system developed in the 1830s by Samuel F. B. Morse, physicist Joseph Henry and Alfred Vail and they developed an electrical telegraph system which sent pulses of electric current along wires which controlled an electromagnet that was located at the receiving end of the telegraph system. A code was needed to transmit natural language using only these pulses, Morse therefore developed the forerunner to modern International Morse code. Audio broadcasting began experimentally in the first decade of the 20th century, by the early 1920s radio broadcasting became a household medium, at first on the AM band and later on FM. Television broadcasting started experimentally in the 1920s and became widespread after World War II, satellite broadcasting was initiated in the 1960s and moved into general industry usage in the 1970s, with DBS emerging in the 1980s. Originally all broadcasting was composed of signals using analog transmission techniques but in the 2000s. In general usage, broadcasting most frequently refers to the transmission of information, Analog audio vs. HD Radio Analog television vs.9 zettabytes. This is the equivalent of 55 newspapers per person per day in 1986. Historically, there have been several methods used for broadcasting electronic media audio and/or video to the public, Telephone broadcasting. Telephone broadcasting also grew to include telephone services for news and entertainment programming which were introduced in the 1890s. These telephone-based subscription services were the first examples of electrical/electronic broadcasting, Radio broadcasting, audio signals sent through the air as radio waves from a transmitter, picked up by an antenna and sent to a receiver
15.
Television
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Television or TV is a telecommunication medium used for transmitting moving images in monochrome, or in color, and in two or three dimensions and sound. The term can refer to a set, a television program. Television is a medium for entertainment, education, news, politics, gossip. Television became available in experimental forms in the late 1920s. After World War II, a form of black-and-white TV broadcasting became popular in the United States and Britain, and television sets became commonplace in homes, businesses. During the 1950s, television was the medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in the US, for many reasons, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions greatly increased in popularity, another development was the move from standard-definition television to high-definition television, which provides a resolution that is substantially higher. HDTV may be transmitted in various formats, 1080p, 1080i, in 2013, 79% of the worlds households owned a television set. Most TV sets sold in the 2000s were flat-panel, mainly LEDs, major manufacturers announced the discontinuation of CRT, DLP, plasma, and even fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are gradually expected to be replaced by OLEDs, also, major manufacturers have announced that they will increasingly produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s, Television signals were initially distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by cable or optical fiber, satellite systems and. Until the early 2000s, these were transmitted as analog signals, a standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is correctly called a video monitor rather than a television, the word television comes from Ancient Greek τῆλε, meaning far, and Latin visio, meaning sight. The Anglicised version of the term is first attested in 1907 and it was. formed in English or borrowed from French télévision. In the 19th century and early 20th century, other. proposals for the name of a technology for sending pictures over distance were telephote. The abbreviation TV is from 1948, the use of the term to mean a television set dates from 1941
16.
Film
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A film, also called a movie, motion picture, theatrical film or photoplay, is a series of still images which, when shown on a screen, creates the illusion of moving images due to the phi phenomenon. This optical illusion causes the audience to perceive continuous motion between separate objects viewed rapidly in succession, the process of filmmaking is both an art and an industry. The word cinema, short for cinematography, is used to refer to the industry of films. Films were originally recorded onto plastic film through a photochemical process, the adoption of CGI-based special effects led to the use of digital intermediates. Most contemporary films are now fully digital through the process of production, distribution. Films recorded in a form traditionally included an analogous optical soundtrack. It runs along a portion of the film exclusively reserved for it and is not projected, Films are cultural artifacts created by specific cultures. They reflect those cultures, and, in turn, affect them, Film is considered to be an important art form, a source of popular entertainment, and a powerful medium for educating—or indoctrinating—citizens. The visual basis of film gives it a power of communication. Some films have become popular worldwide attractions by using dubbing or subtitles to translate the dialog into the language of the viewer, some have criticized the film industrys glorification of violence and its potentially negative treatment of women. The individual images that make up a film are called frames, the perception of motion is due to a psychological effect called phi phenomenon. The name film originates from the fact that film has historically been the medium for recording and displaying motion pictures. Many other terms exist for a motion picture, including picture, picture show, moving picture, photoplay. The most common term in the United States is movie, while in Europe film is preferred. Terms for the field, in general, include the big screen, the screen, the movies, and cinema. In early years, the sheet was sometimes used instead of screen. Preceding film in origin by thousands of years, early plays and dances had elements common to film, scripts, sets, costumes, production, direction, actors, audiences, storyboards, much terminology later used in film theory and criticism apply, such as mise en scène. Owing to the lack of any technology for doing so, the moving images, the magic lantern, probably created by Christiaan Huygens in the 1650s, could be used to project animation, which was achieved by various types of mechanical slides
17.
Post-production
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Post-production, or postproduction, is part of the process of filmmaking, video production, and photography. It occurs in the making of pictures, television programs, radio programs, advertising, audio recordings, photography. It is a term for all stages of production occurring after shooting or recording individual program segments, traditional post-production has been eroded away by video editing software that operates on a non-linear editing system. Post-production is many different processes grouped under one name and these typically include, Video editing the picture of a television program using an edit decision list Writing, recording, and editing the soundtrack. Adding visual special effects - mainly computer-generated imagery and digital copy from which release prints will be made, sound design, sound effects, ADR, foley, and music, culminating in a process known as sound re-recording or mixing with professional audio equipment. Transfer of colour motion picture film to video or DPX with a telecine, the process of editing a movie is also seen as the second directing because through post-production it is possible to change the intention of the movie. Furthermore, through the use of color grading tools and the addition of music and sound, for instance, a blue-tinted movie is associated with a cold atmosphere and the choice of music and sound increases the effect of the shown scenes to the audience. Post-production was named a dying industry by Phil Izzo, the once exclusive service offered by high-end post-production facilities have been eroded away by video editing software that operates on a non-linear editing system. As such, traditional services are being surpassed by digital. In television, the phases of post-production include, editing, video editing, sound editing, animation and visual effects insertions, viewing and it is imperative that post-production executes and oversees the preparation until the final product is completely ready. Professional post-producers usually apply a certain range of image editing operations to the raw image format provided by a photographer or an image-bank, there is a range of proprietary and free and open-source software, running on a range of operating systems available to do this work. The first stage of post-production usually requires loading the RAW images into the post-production software, if there is more than one image, and they belong to a set, ideally post-producers try to equalize the images before loading them. After that, if necessary, the step would be to cut the objects in the images with the Pen Tool for a perfect. The next stage would be cleaning the image using tools such as the tool, clone tool. The next stages depend on what the client ordered, if its a photo-montage, the post-producers would usually start assembling the different images into the final document, and start to integrate the images with the background. In advertising, it usually requires assembling several images together in a photo-composition, types of work usually done, Advertising that requires one background and one or more models. Fashion photography that usually requires a really heavy post-production for editorial and/or advertising, techniques used in music post-production include comping, timing and pitch correction, and adding effects. This process is referred to as mixing and can also involve equalization
18.
Loudspeaker
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A loudspeaker is an electroacoustic transducer, which converts an electrical audio signal into a corresponding sound. The most widely used type of speaker in the 2010s is the speaker, invented in 1925 by Edward W. Kellogg. The dynamic speaker operates on the basic principle as a dynamic microphone. Besides this most common method, there are several technologies that can be used to convert an electrical signal into sound. The sound source must be amplified or strengthened with a power amplifier before the signal is sent to the speaker. Speakers are typically housed in an enclosure or speaker cabinet which is often a rectangular or square box made of wood or sometimes plastic. The enclosures materials and design play an important role in the quality of the sound, where high fidelity reproduction of sound is required, multiple loudspeaker transducers are often mounted in the same enclosure, each reproducing a part of the audible frequency range. In this case the individual speakers are referred to as drivers, drivers made for reproducing high audio frequencies are called tweeters, those for middle frequencies are called mid-range drivers, and those for low frequencies are called woofers. Smaller loudspeakers are found in such as radios, televisions, portable audio players, computers. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, the term loudspeaker may refer to individual transducers or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a range of frequencies with even coverage, most loudspeaker systems employ more than one driver. Individual drivers are used to different frequency ranges. The drivers are named subwoofers, woofers, mid-range speakers, tweeters, the terms for different speaker drivers differ, depending on the application. In two-way systems there is no mid-range driver, so the task of reproducing the mid-range sounds falls upon the woofer and tweeter, home stereos use the designation tweeter for the high frequency driver, while professional concert systems may designate them as HF or highs. When multiple drivers are used in a system, a network, called a crossover. Loudspeaker driver of the type pictured are termed dynamic to distinguish them from earlier drivers, or speakers using piezoelectric or electrostatic systems, or any of several other sorts. Johann Philipp Reis installed an electric loudspeaker in his telephone in 1861, it was capable of reproducing clear tones, alexander Graham Bell patented his first electric loudspeaker as part of his telephone in 1876, which was followed in 1877 by an improved version from Ernst Siemens. In 1898, Horace Short patented a design for a loudspeaker driven by compressed air, he sold the rights to Charles Parsons
19.
DJ mixer
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A DJ mixer is a type of audio mixing console used by DJs to make smooth transitions between different sound recordings as they are playing. The sources are typically record turntables, compact cassettes, CDJs, DJ mixers allow the DJ to use headphones to preview the next song before playing it to the audience. Most low- to mid-priced DJ mixers can accommodate two turntables or CD players, but some mixers can accommodate up to four turntables or CD players. A crossfader has the engineering design as a fader, in that it is a sliding control, but unlike faders. DJ mixers typically have phono preamplifiers to hook up turntables, DJ mixers are also used to create DJ mixes, which are recorded and sold. DJ mixers usually have controls for bass and treble of each channel. Some 2010-era DJ mixers have onboard electronic or digital effects such as echo or reverb. Some DJ mixers also feature a built-in USB sound card to connect to a computer running DJ software without requiring a separate sound card. DJ mixers typically have an input, so that a microphone can be plugged into the mixer. Some DJ mixers have a kill switch, the output from a DJ mixer is typically plugged into a sound reinforcement system or a PA system at a dance, rave, nightclub or similar venue or event. If the DJ is performing a mix for a station or television station. At club sets, some DJs may use a monitor speaker to hear the main mix. This monitor speaker can have its volume increased or decreased as needed, DJ mixers have a plug that is connected to the wall to supply electric power for the unit. DJ mixing played a key role in the development of hip hop music, in hip hop music and occasionally in other genres, the turntable is used as a musical instrument by DJs, who use turntables along with a DJ mixer to create unique rhythmic sounds. Manipulation of a record as part of the music, rather than for normal playback or mixing, is called turntablism, the basis of turntablism, and its best known technique, is scratching, pioneered by Grand Wizzard Theodore. It was not until Herbie Hancocks Rockit in 1983 that the movement was recognized in popular music outside of a hip hop context. In the 2010s, many hip hop DJs use DJ CD players or digital record emulator devices to create scratching sounds, nevertheless, DJ mixing also played a key role in disco music in the 1970s. In disco clubs, DJs would use mixers to transition from one song to another, one of the pioneers of DJ mixing equipment design was Rudy Bozak
20.
Phonograph
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The phonograph is a device invented in 1877 for the mechanical recording and reproduction of sound. In its later forms it is called a gramophone. To recreate the sound, the surface is rotated while a playback stylus traces the groove and is therefore vibrated by it. In later electric phonographs, the motions of the stylus are converted into an electrical signal by a transducer. The phonograph was invented in 1877 by Thomas Edison, while other inventors had produced devices that could record sounds, Edisons phonograph was the first to be able to reproduce the recorded sound. His phonograph originally recorded sound onto a sheet wrapped around a rotating cylinder. A stylus responding to sound vibrations produced an up and down or hill-and-dale groove in the foil, in the 1890s, Emile Berliner initiated the transition from phonograph cylinders to flat discs with a spiral groove running from the periphery to near the center. Later improvements through the years included modifications to the turntable and its system, the stylus or needle. The disc phonograph record was the dominant audio recording format throughout most of the 20th century, from the mid-1980s on, phonograph use on a standard record player declined sharply because of the rise of the cassette tape, compact disc and other digital recording formats. Records are still a favorite format for some audiophiles and DJs, vinyl records are still used by some DJs and musicians in their concert performances. Musicians continue to release their recordings on vinyl records, the original recordings of musicians are sometimes re-issued on vinyl. Usage of terminology is not uniform across the English-speaking world, in more modern usage, the playback device is often called a turntable, record player, or record changer. When used in conjunction with a mixer as part of a DJ setup, the term phonograph was derived from the Greek words φωνή and γραφή. The similar related terms gramophone and graphophone have similar root meanings, the roots were already familiar from existing 19th-century words such as photograph, telegraph, and telephone. In British English, gramophone may refer to any sound-reproducing machine using disc records, the term phonograph was usually restricted to machines that used cylinder records. Gramophone generally referred to a wind-up machine, after the introduction of the softer vinyl records, 33 1⁄3-rpm LPs and 45-rpm single or two-song records, and EPs, the common name became record player or turntable. Often the home record player was part of a system that included a radio and, later, from about 1960, such a system began to be described as a hi-fi or a stereo. In American English, phonograph, properly specific to machines made by Edison, was used in a generic sense as early as the 1890s to include cylinder-playing machines made by others
21.
Coffeehouse
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A coffeehouse, coffee shop, or café is an establishment which primarily serves hot coffee, related coffee beverages, tea, and other hot beverages. Some coffeehouses also serve cold beverages such as iced coffee and iced tea, many cafés also serve some type of food, such as light snacks, muffins, or pastries. Coffeehouses range from owner-operated small businesses to multinational corporations. A coffeehouse may share some of the characteristics of a bar or restaurant. Many coffee houses in the Middle East and in West Asian immigrant districts in the Western world offer shisha, espresso bars are a type of coffeehouse that specializes in serving espresso and espresso-based drinks. Since the development of Wi-Fi, coffeehouses with this capability have also become places for patrons to access the Internet on their laptops, a coffeehouse can serve as an informal club for its regular members. As early as the 1950s Beatnik era and the 1960s folk music scene, coffeehouses have hosted singer-songwriter performances, coffeehouses in Mecca became a concern as places for political gatherings to the imams, who banned them, as well as the drink, for Muslims between 1512 and 1524. In 1530, the first coffeehouse was opened in Damascus and not long there were many coffeehouses in Cairo. About that year, a fellow called Hakam from Aleppo and a wag called Shams from Damascus came to the city, they opened a large shop in the district called Tahtakale. Various legends involving the introduction of coffee to Istanbul at a Kiva Han in the late 15th century circulate in culinary tradition, resembling checkers, hopscotch, and chess, are played. In addition, mollas, dervishes, and poets take turns telling stories in verse or in prose, the narrations by the mollas and the dervishes are moral lessons, like our sermons, but it is not considered scandalous not to pay attention to them. No one is forced to give up his game or his conversation because of it. It often happens that two or three people talk at the time, one on one side, the other on the opposite, and sometimes one will be a preacher. The most common English spelling, café, is the French, Portuguese and Spanish spelling, thus the spelling cafe has become very common in English-language usage throughout the world, especially for the less formal, i. e. greasy spoon variety. The Italian spelling, caffè, is sometimes used in English. In southern England, especially around London in the 1950s, the French pronunciation was often altered to /ˈkæf/. The English words coffee and café both descend from the Italian word for coffee, caffè—first attested as caveé in Venice in 1570— and in turn derived from the Arabic qahuwa. The Arabic term qahuwa originally referred to a type of wine but after the ban by Mohammed
22.
Rock music
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It has its roots in 1940s and 1950s rock and roll, itself heavily influenced by blues, rhythm and blues and country music. Rock music also drew strongly on a number of genres such as electric blues and folk. Musically, rock has centered on the guitar, usually as part of a rock group with electric bass guitar. Typically, rock is song-based music usually with a 4/4 time signature using a verse-chorus form, like pop music, lyrics often stress romantic love but also address a wide variety of other themes that are frequently social or political in emphasis. Punk was an influence into the 1980s on the subsequent development of subgenres, including new wave, post-punk. From the 1990s alternative rock began to rock music and break through into the mainstream in the form of grunge, Britpop. Similarly, 1970s punk culture spawned the visually distinctive goth and emo subcultures and this trio of instruments has often been complemented by the inclusion of other instruments, particularly keyboards such as the piano, Hammond organ and synthesizers. The basic rock instrumentation was adapted from the blues band instrumentation. A group of musicians performing rock music is termed a rock band or rock group, Rock music is traditionally built on a foundation of simple unsyncopated rhythms in a 4/4 meter, with a repetitive snare drum back beat on beats two and four. Melodies are often derived from older musical modes, including the Dorian and Mixolydian, harmonies range from the common triad to parallel fourths and fifths and dissonant harmonic progressions. Critics have stressed the eclecticism and stylistic diversity of rock, because of its complex history and tendency to borrow from other musical and cultural forms, it has been argued that it is impossible to bind rock music to a rigidly delineated musical definition. These themes were inherited from a variety of sources, including the Tin Pan Alley pop tradition, folk music and rhythm, as a result, it has been seen as articulating the concerns of this group in both style and lyrics. Christgau, writing in 1972, said in spite of some exceptions, rock and roll usually implies an identification of male sexuality, according to Simon Frith rock was something more than pop, something more than rock and roll. Rock musicians combined an emphasis on skill and technique with the concept of art as artistic expression, original. The foundations of music are in rock and roll, which originated in the United States during the late 1940s and early 1950s. Its immediate origins lay in a melding of various musical genres of the time, including rhythm and blues and gospel music, with country. In 1951, Cleveland, Ohio disc jockey Alan Freed began playing rhythm and blues music for a multi-racial audience, debate surrounds which record should be considered the first rock and roll record. Other artists with rock and roll hits included Chuck Berry, Bo Diddley, Fats Domino, Little Richard, Jerry Lee Lewis
23.
Rhythm section
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Many of the rhythm section instruments, such as keyboard instruments and guitars, are also used to play the chord progression upon which the song is based. The bass instrument plays the bassline that supports the chord progression. The term is common in small musical ensembles, such as bands that play jazz, country, blues. In modern rock music, a rhythm guitarist specializes in rhythmic and chordal playing, often repeating quaver, in the louder genres, such as hard rock, heavy metal and punk rock, rhythm guitarists often play power chords with distortion. Rhythm guitarists often strum open chords in pop, rock, country and folk music and play barre chords in many pop, a typical rhythm section comprises one or more guitars, and/or a keyboard instrument a double bass or electric bass, and drums. In some styles of music, there may be additional percussionists playing instruments such as the djembe or shakers, some styles of music often have two electric guitarists, such as rock genres like heavy metal music and punk rock. Some styles of music use multiple keyboard instrument performers simultaneously for a fuller sound, the instrumentalists used in a rhythm section vary according to the style of music and era. Modern pop, rock and jazz band rhythm sections typically consist of a drummer, a bass player, the term rhythm section may also refer to the instruments in this group. In music industry parlance, the amplifiers and some of the instruments are nicknamed the backline, backline instruments are commonly provided for bands at music festivals and other concerts where several bands will play during an event. By providing these backline instruments, this speeds up the process when new bands take the stage. Even when a venue or festival provides a backline, musicians must still supply some instruments themselves, such as guitars, a bass, and, in some cases. Although rhythm sections spend much of the time providing accompaniment for songs, in some cases, in some songs or styles of music, instruments from the rhythm section may play soloistic roles on occasion or play a melodic role. However, since rhythm sections provide the underpinning for a performance by the lead instruments and vocalists. Some of the most accomplished rhythm sections have become famous, such as The Band, The E Street Band and Sly Dunbar, as well, in some popular bands, all of the band members, including rhythm section members, have become famous as individuals. In each style of music, there are different musical approaches and styles that rhythm section members are expected to use, drummers and percussionists are expected to be able to improvise or prepare rhythm parts that suit the style of a given song. In some cases, an arranger, orchestrator or composer will provide a bass part or drum part written in music notation. Rhythm section members may be expected to sing backup vocals or harmony parts in some styles of music, in some types of heavy metal music, rhythm section members may be expected to be able to headbang while performing. Less commonly, some rhythm section members may sing lead vocals, in some groups, one rhythm section member may have other roles, such as bandleader, conductor, songwriter, composer or arranger
24.
Phantom power
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Phantom power, in the context of professional audio equipment, is DC electric power transmitted through microphone cables to operate microphones that contain active electronic circuitry. It is best known as a convenient power source for condenser microphones, the technique is also used in other applications where power supply and signal communication take place over the same wires. Phantom power supplies are often built into mixing consoles, microphone preamplifiers, in addition to powering the circuitry of a microphone, traditional condenser microphones also use phantom power for polarizing the microphones transducer element. Phantom powering was used in telephone systems since the introduction of the telephone in 1919 before it was applied to condenser microphones. One such application in the system was to provide a DC signaling path around transformer connected amplifiers in analogue line transmission systems. In 1966, Neumann GmbH of Berlin, Germany, presented a new type of transistorized microphone to the Norwegian Broadcasting Corporation, Norwegian Radio had requested phantom-powered operation. Since NRK already had 48 V available in their studios for their lighting systems, this voltage was used for powering the new microphones. This arrangement was standardized in DIN45596. Phantom powering consists of a circuit where direct current is applied equally through the two signal lines of a balanced audio connector. The supply voltage is referenced to the pin of the connector. This is in contrast to microphones with vacuum-tube circuitry, most of which require special, with phantom power, the supply voltage is effectively invisible to balanced microphones that do not use it, which includes most dynamic microphones. A balanced signal consists only of the differences in voltage between two lines, phantom powering places the same DC voltage on both signal lines of a balanced connection. This is in marked contrast to another, slightly earlier method of powering known as parallel powering or T-powering, connecting a conventional microphone to an input that had parallel powering enabled could very well damage the microphone. The prevailing international standard, IEC61938, defines 48-volt, 24-volt, the signal conductors are positive, both fed through resistors of equal value, and the shield is ground. The 6.81 kΩ value is not critical, but the resistors must be matched to within 0. 1% or better to maintain good common-mode rejection in the circuit. If it is desired to disconnect phantom power from one channel only, instrument amplifiers rarely provide phantom power. To use equipment requiring it with these amplifiers, a power supply must be inserted into the line. These are readily available commercially, or alternatively are one of the projects for the amateur electronics constructor
25.
Filter (signal processing)
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In signal processing, a filter is a device or process that removes some unwanted components or features from a signal. Filtering is a class of processing, the defining feature of filters being the complete or partial suppression of some aspect of the signal. Most often, this means removing some frequencies and not others in order to suppress interfering signals, however, filters do not exclusively act in the frequency domain, especially in the field of image processing many other targets for filtering exist. Correlations can be removed for certain components and not for others without having to act in the frequency domain. There are many different bases of classifying filters and these overlap in many different ways, Filters may be, linear or non-linear time-invariant or time-variant, also known as shift invariance. If the filter operates in a spatial domain then the characterization is space invariance, causal or not-causal, A filter is non-causal if its present output depends on future input. Filters processing time-domain signals in real time must be causal, Analog or digital discrete-time or continuous-time passive or active type of continuous-time filter infinite impulse response or finite impulse response type of discrete-time or digital filter. Linear continuous-time circuit is perhaps the most common meaning for filter in the signal processing world and these circuits are generally designed to remove certain frequencies and allow others to pass. Circuits that perform this function are generally linear in their response, any nonlinearity would potentially result in the output signal containing frequency components not present in the input signal. The modern design methodology for linear continuous-time filters is called network synthesis, some important filter families designed in this way are, Chebyshev filter, has the best approximation to the ideal response of any filter for a specified order and ripple. Butterworth filter, has a flat frequency response. Bessel filter, has a flat phase delay. Elliptic filter, has the steepest cutoff of any filter for a specified order, the difference between these filter families is that they all use a different polynomial function to approximate to the ideal filter response. This results in each having a different transfer function, another older, less-used methodology is the image parameter method. Filters designed by this methodology are archaically called wave filters, some important filters designed by this method are, Constant k filter, the original and simplest form of wave filter. M-derived filter, a modification of the constant k with improved cutoff steepness, high-pass filter – high frequencies are passed, low frequencies are attenuated. Band-pass filter – only frequencies in a band are passed. Band-stop filter or band-reject filter – only frequencies in a band are attenuated
26.
Equalization (audio)
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Equalization is the process of adjusting the balance between frequency components within an electronic signal. The most well known use of equalization is in recording and reproduction but there are many other applications in electronics. The circuit or equipment used to achieve equalization is called an equalizer and these devices strengthen or weaken the energy of specific frequency bands or frequency ranges. In sound recording and reproduction, equalization is the commonly used to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments, graphic and parametric equalizers have much more flexibility in tailoring the frequency content of an audio signal. An equalizer is the circuit or equipment used to achieve equalization, since equalizers, adjust the amplitude of audio signals at particular frequencies, they are, in other words, frequency-specific volume knobs. The term EQ specifically refers to this variant of the term, stereos and basic guitar amplifiers typically have adjustable equalizers which boost or cut bass or treble frequencies. Mid- to high-priced guitar and bass amplifiers usually have more bands of frequency control, such as bass, mid-range and treble or bass, low-mid, high-mid, some amps have an additional knob for controlling very high frequencies. Broadcast and recording studios use sophisticated equalizers capable of more detailed adjustments. The most common equalizers in music production are parametric, semi-parametric, graphic, peak, graphic equalizers are often included in consumer audio equipment and software which plays music on home computers. Parametric equalizers require more expertise than graphic equalizers, and they can provide more specific compensation or alteration around a chosen frequency and this may be used in order to remove unwanted resonances or boost certain frequencies. An acoustic guitarist who finds that her instrument sounds too boomy may ask the engineer to reduce the low frequency range response. A guitarist who finds that the instrument sound in the PA has too much finger noise may ask the engineer to reduce the frequency range response. The concept of equalization was first applied in correcting the frequency response of telephone lines using passive networks, a plot of the systems net frequency response would be flat, as its response to all frequencies would literally be equal. Much later the concept was applied in engineering to adjust the frequency response in recording, reproduction. Audio amplifiers have long had filters or controls to modify their frequency response and these are most often in the form of variable bass and treble controls, and switches to apply low-cut or high-cut filters for elimination of low frequency rumble and high frequency hiss respectively. Graphic equalizers and other equipment developed for improving fidelity have since used by recording engineers to modify frequency responses for aesthetic reasons. Hence in the field of audio electronics the term equalization is now used to describe the application of such filters regardless of intent
27.
Dynamic range compression
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Compression is commonly used in sound recording and reproduction, broadcasting, live sound reinforcement and in some instrument amplifiers. A dedicated electronic hardware unit or audio software that applies compression is called a compressor, in the 2000s, compressors became available as software plugins that run in digital audio workstation software. In recorded and live music, compression parameters may be adjusted to change the way they affect sounds, compression and limiting are identical in process but different in degree and perceived effect. A limiter is a compressor with a ratio and, generally. Downward compression reduces loud sounds over a certain threshold while quiet sounds remain unaffected, upward compression increases the loudness of sounds below a certain threshold while leaving louder sounds unaffected. Both downward and upward compression reduce the range of an audio signal. An expander performs the function, increasing the dynamic range of the audio signal. Expanders are generally used to make quiet sounds even quieter by reducing the level of a signal that falls below a set threshold level. A noise gate is a type of expander and this design, known as a feed-forward type, is used today in most compressors. Earlier designs were based on a layout where the signal level was measured after the amplifier. There are a number of used for variable-gain amplification, each having different advantages and disadvantages. Vacuum tubes are used in a configuration called variable-mu where the voltage changes to alter the gain. Optical compressors use a photoresistor and a lamp to create changes in signal gain. This technique is believed by some to sound smoother because the times of the light. Other technologies used include field effect transistors and a diode bridge, when working with digital audio, digital signal processing techniques are commonly used to implement compression via digital audio editors, or dedicated workstations. Often the algorithms used emulate the above analog technologies, a compressor reduces the level of an audio signal if its amplitude exceeds a certain threshold. It is commonly set in decibels dB, where a lower threshold means a portion of the signal is treated. The amount of reduction is determined by ratio, a ratio of 4,1 means that if input level is 4 dB over the threshold
28.
Audio power amplifier
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This includes both amplifiers used in home audio systems and musical instrument amplifiers like guitar amplifiers. It is the electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers. The inputs can also be any number of sources like record players, CD players, digital audio players. Most audio power amplifiers require these low-level inputs, which are line level, the audio amplifier was invented in 1909 by Lee De Forest when he invented the triode vacuum tube. The triode was a three terminal device with a grid that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the first AM radio, early audio power amplifiers were based on vacuum tubes and some of these achieved notably high audio quality. Audio power amplifiers based on transistors became practical with the availability of inexpensive transistors in the late 1960s. Since the 1970s, most modern audio amplifiers are based on solid state devices, transistor-based amplifiers are lighter in weight, more reliable and require less maintenance than tube amplifiers. In the 2010s, there are still audio enthusiasts, musicians, audio engineers and music producers who prefer tube-based amplifiers, key design parameters for audio power amplifiers are frequency response, gain, noise, and distortion. These are interdependent, increasing gain often leads to increases in noise. While negative feedback reduces the gain, it also reduces distortion. Most audio amplifiers are linear amplifiers operating in class AB, until the 1970s, most amplifiers were tube amplifiers which used vacuum tubes. During the 1970s, tube amps were increasingly replaced with transistor-based amplifiers, which were lighter in weight, more reliable, one alternative to a separate preamp is to simply use passive volume and switching controls, sometimes integrated into a power amplifier to form an integrated amplifier. The final stage of amplification, after preamplifiers, is the output stage, for this reason, the design choices made around the output device or devices, such as the Class of operation of the output devices is often taken as the description of the whole power amplifier. For example, a Class B amplifier will probably have just the power output devices operating cut off for half of each cycle, while the other devices operate in Class A. In a transformerless output stage, the devices are essentially in series with the supply and output load. For some years following the introduction of solid state amplifiers, their perceived sound did not have the excellent audio quality of the best valve amplifiers and this led audiophiles to believe that tube sound or valve sound had an intrinsic quality due to the vacuum tube technology itself. In 1970, Matti Otala published a paper on the origin of a previously unobserved form of distortion, transient intermodulation distortion, TIM distortion was found to occur during very rapid increases in amplifier output voltage
29.
Monaural
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Monaural or monophonic sound reproduction is intended to be heard as if it were a single channel of sound perceived as coming from one position. Monaural recordings, like stereo, customarily use multiple microphones, fed into multiple channels on a recording console, in some cases the multitrack source is mixed down to a one track tape becoming one signal. However, today monaural recordings are usually mastered to be played on stereo and multi-track formats, monaural sound has been replaced by stereo sound in most entertainment applications. However, it remains the standard for communications, telephone networks. A few FM radio stations, particularly talk radio shows, choose to broadcast in monaural, as a monaural signal has a slight advantage in signal strength over a stereophonic signal of the same power. Monaural sound is normal on, Phonograph cylinders Disc records made before 1958, such as made for playing at a speed of 78 rpm and earlier 16 2⁄3, 33 1⁄3. Some FM radio stations that broadcast only spoken word or talk radio content in order to maximize their coverage area, examples of this would be the CBC Radio One stations on the FM dial. Sometimes listeners will not be convinced that the signal is strong since there is no ST or STEREO LED lit, subcarrier signals for FM radio, which carry leased content such as background music for businesses or a radio reading service for the blind. Background music services such as Seeburg 1000, satellite broadcasts by Muzak as well as the public systems such services are intended to be used with. At various times artists have preferred to work in mono, either in recognition of the limitations of the equipment of the era or because of simple preference. Many of Stanley Kubrick and Woody Allens movies were recorded in mono because of their directors preferences, monaural LP records were eventually phased out and no longer manufactured after the early 1970s, with a few exceptions. For example, Decca UK had a few double issues until the end of 1970-the last one being Tom Joness I Who Have Nothing, during the 1960s it was common for albums to be released as both monaural LPs and stereo LPs, occasionally with slight differences between the two. This was because many people owned mono record players that were incapable of playing stereo records, on 9 September 2009, The Beatles re-released a remastered box set of their mono output spanning the Please Please Me album to The Beatles. The set, simply called The Beatles in Mono, also includes a summary of the mono singles, B-sides. Also included were five tracks originally mixed for an unissued mono Yellow Submarine EP, Bob Dylan followed suit on October 19,2010 with The Original Mono Recordings, a box set featuring the mono releases from Bob Dylan to John Wesley Harding. When the initial run of the box set sold out, no more were pressed, unlike the Beatles, sometimes mono sound or monaural can simply refer to a merged pair of stereo channels - also known as collapsed stereo or folded-down stereo. Over time some devices have used mono sound amplification circuitry with two or more speakers since it can cut the cost of the hardware, some consumer electronics with stereo RCA outputs have a microswitch in the red RCA output that disables merging of stereo sound into the white RCA output. Common devices with this are VCRs, DVD/Blu-ray players, information appliances, set-top boxes, video game consoles sometimes have male RCA ends of cables with a proprietary multi-A/V plug on the other end, which prevents automatic stereo merging unless adapters are used
30.
Stereophonic sound
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Stereophonic sound or, more commonly, stereo, is a method of sound reproduction that creates an illusion of multi-directional audible perspective. Thus the term applies to so-called quadraphonic and surround-sound systems as well as the more common two-channel. It is often contrasted with monophonic, or mono sound, where audio is heard as coming from one position, in the 2000s, stereo sound is common in entertainment systems such as broadcast radio and TV, recorded music and the cinema. The word stereophonic derives from the Greek στερεός, firm, solid + φωνή, sound, tone, voice and it was coined in 1927 by Western Electric, the signal is then reproduced over multiple loudspeakers to recreate, as closely as possible, the live sound. Secondly artificial or pan-pot stereo, in which a sound is reproduced over multiple loudspeakers. By varying the amplitude of the signal sent to each speaker an artificial direction can be suggested. The control which is used to vary this relative amplitude of the signal is known as a pan-pot, by combining multiple pan-potted mono signals together, a complete, yet entirely artificial, sound field can be created. In technical usage, true stereo sound recording and sound reproduction that uses stereographic projection to encode the relative positions of objects and events recorded. During two-channel stereo recording, two microphones are placed in strategically chosen locations relative to the source, with both recording simultaneously. The two recorded channels will be similar, but each will have distinct time-of-arrival and sound-pressure-level information, during playback, the listeners brain uses those subtle differences in timing and sound level to triangulate the positions of the recorded objects. Stereo recordings often cannot be played on systems without a significant loss of fidelity. This phenomenon is known as phase cancellation and this two-channel telephonic process was commercialized in France from 1890 to 1932 as the Théâtrophone, and in England from 1895 to 1925 as the Electrophone. Both were services available by coin-operated receivers at hotels and cafés, modern stereophonic technology was invented in the 1930s by British engineer Alan Blumlein at EMI, who patented stereo records, stereo films, and also surround sound. In early 1931, Blumlein and his wife were at a local cinema, Blumlein declared to his wife that he had found a way to make the sound follow the actor across the screen. The genesis of ideas is uncertain, but he explained them to Isaac Shoenberg in the late summer of 1931. His earliest notes on the subject are dated 25 September 1931, the application was dated 14 December 1931, and was accepted on 14 June 1933 as UK patent number 394,325. The patent covered many ideas in stereo, some of which are used today and these discs used the two walls of the groove at right angles in order to carry the two channels. Much of the development work on this system for cinematic use did not reach completion until 1935, in Blumleins short test films, his original intent of having the sound follow the actor was fully realised
31.
Potentiometer
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A potentiometer, informally a pot, is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a resistor or rheostat. The measuring instrument called a potentiometer is essentially a voltage divider used for measuring electric potential, potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. Potentiometers operated by a mechanism can be used as transducers, for example. Potentiometers are rarely used to control significant power, since the power dissipated in the potentiometer would be comparable to the power in the controlled load. The resistive element can be flat or angled, each end of the resistive element is connected to a terminal on the case. The wiper is connected to a terminal, usually between the other two. On panel potentiometers, the wiper is usually the terminal of three. For single-turn potentiometers, this wiper typically travels just under one revolution around the contact, the only point of ingress for contamination is the narrow space between the shaft and the housing it rotates in. Another type is the slider potentiometer, which has a wiper which slides along a linear element instead of rotating. Contamination can potentially enter anywhere along the slot the slider moves in, making effective sealing more difficult, an advantage of the slider potentiometer is that the slider position gives a visual indication of its setting. The resistive element of inexpensive potentiometers is often made of graphite, other materials used include resistance wire, carbon particles in plastic, and a ceramic/metal mixture called cermet. Others are enclosed within the equipment and are intended to be adjusted to calibrate equipment during manufacture or repair and they are usually physically much smaller than user-accessible potentiometers, and may need to be operated by a screwdriver rather than having a knob. They are usually called preset potentiometers or trim pots, some presets are accessible by a small screwdriver poked through a hole in the case to allow servicing without dismantling. Multiturn potentiometers are also operated by rotating a shaft, but by several turns rather than less than a full turn, a string potentiometer is a multi-turn potentiometer operated by an attached reel of wire turning against a spring, enabling it to convert linear position to a variable resistance. User-accessible rotary potentiometers can be fitted with a switch which operates usually at the extreme of rotation. Multiple resistance elements can be ganged together with their contacts on the same shaft, for example. The relationship between position and resistance, known as the taper or law, is controlled by the manufacturer
32.
Fade (audio engineering)
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In audio engineering, a fade is a gradual increase or decrease in the level of an audio signal. The term can also be used for film cinematography or theatre lighting in much the same way, a recorded song may be gradually reduced to silence at its end, or may gradually increase from silence at the beginning. Fading-out can serve as a solution for pieces of music that contain no obvious ending. Both fades and cross-fades are very valuable since they allow the engineer to quickly and easily make sure that the beginning and it is necessary that there is a clear section of silence prior to the audio. Fade-ins and out can also be used to change the characteristics of a sound, for example a fade-in is used to soften the attack and it can also be used to soften up the attack of the drum and/or percussion instruments. A cross-fade can be manipulated through its rates and coefficients in order to create different styles of fading, almost every fade is different, this means that the fade parameters must be adjusted according to the individual needs of the mix. Club DJs in house music and techno use DJ mixers, two or more sound sources along with a skill called beatmatching to make seamless dance mixes for dancers at raves, nightclubs, though relatively rare, songs can fade out then fade back in. 2 by Argent and Future by Paramore, possibly the earliest example of a fade-out ending can be heard in Joseph Haydns Symphony No. 45, nicknamed the Farewell Symphony on account of the fade-out ending and this was expressed by the players extinguishing their stand candles and leaving the stage one by one during the final adagio movement of the symphony, leaving only two muted violins playing. Esterhazy appears to have understood the message, allowing the musicians to leave, gustav Holsts Neptune, the mystic, part of the orchestral suite The Planets written between 1914 and 1916, is another early example of music to have a fade-out ending during performance. Until the imagination knew no difference between sound and silence, the technique of ending a spoken or musical recording by fading out the sound goes back to the earliest days of recording. This is called the “Pulse Continuity Phenomenon and was measured by a task to measure participants’ perception of pulsation. An 189478 rpm record called The Spirit of 76, a narrated musical vignette with martial fife-and-drum that gets louder as it nears the listener and quieter as it moves away, there are early examples that appear to bear no obvious relationship to movement. One is Barkin Dog by the Ted Lewis Jazz Band, another contender is America, a patriotic piece by the chorus of evangelist Billy Sunday. By the early 1930s longer songs were being put on both sides of records, with the fading out at the end of Side One. Records at the time only about two to five minutes of music per side. The segue allowed for longer songs, symphonies and live concert recordings, however, shorter songs continued to use the fade-out for unclear reasons—for example, Fred Astaires movie theme Flying Down to Rio. Even using fade-out as a segue device doesnt seem obvious, though we certainly take it for granted today and it is possible that movies were an influence here
33.
Preamplifier
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Without this, the final signal would be noisy or distorted. They are typically used to amplify signals from analog sensors such as microphones, because of this, the preamplifier is often placed close to the sensor to reduce the effects of noise and interference. An ideal preamp will be linear, have input impedance. It is used to boost the strength to drive the cable to the main instrument without significantly degrading the signal-to-noise ratio. The noise performance of a preamplifier is critical, according to Friiss formula, when the gain of the preamplifier is high, the SNR of the final signal is determined by the SNR of the input signal and the noise figure of the preamplifier. Three basic types of preamplifiers are available, current-sensitive preamplifier parasitic-capacitance preamplifier charge-sensitive preamplifier, in an audio system, they are typically used to amplify signals from analog sensors to line level. The second amplifier is typically a power amplifier, the preamplifier provides voltage gain but no significant current gain. The power amplifier provides the current necessary to drive loudspeakers. For these systems some common sensors are microphones, instrument pickups, preamplifiers are often integrated into the audio inputs on mixing consoles, DJ mixers, and sound cards. They can also be stand-alone devices, the integrated pre-amplifier in a foil electret microphone. The first stages of an instrument amplifier, which is sent to the power amplifier. With instrument amplifiers, the preamp is often designed to produce overdrive or distortion effects, a stand-alone unit for use in live music and recording studio applications. As part of a stand-alone channel strip or channel strip built into a mixing desk. A masthead amplifier used with television receiver antenna or a satellite receiver dish, the circuit inside of a hard drive connected to the magnetic heads or the circuit inside of CD/DVD drive which connects to the photodiodes
34.
XLR connector
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The XLR connector is a style of electrical connector, primarily found on professional audio, video, and stage lighting equipment. The connectors are circular in design and have between 3 and 7 pins and they are most commonly associated with balanced audio interconnection, including AES3 digital audio, but are also used for lighting control, low-voltage power supplies, and other applications. XLR connectors are available from a number of manufacturers and are covered by a standard for dimensions. They are superficially similar to the older and smaller DIN connector range, a smaller version, the Mini XLR Connector, is used on smaller equipment. The XLR connector was invented by James H, there was also an XLP series which used a hard plastic insulation, but was otherwise the same. ITT Cannon originally manufactured XLR connectors in two locations Kanagawa, Japan and Melbourne, Australia, the Australian operation was sold to Alcatel Components in 1992 and then acquired by Amphenol in 1998. ITT Cannon continues to manufacture XLR connectors in Japan, the Switchcraft corporation later started manufacturing compatible connectors, followed by Neutrik. These improvements have made Neutrik the most popular brand of XLR connector, unbranded XLRs are also made by East Asian manufacturers. Originally these were copies of the Cannon or Switchcraft designs, XLR connectors are available in male and female versions in both cable and chassis mounting designs, a total of four styles. This is slightly unusual as many other connector designs omit one of the styles, the female XLR connectors are designed to first connect pin 1, before the other pins make contact, when a male XLR connector is inserted. With the ground connection established before the lines are connected. As of 2016, XLR connectors are available with up to 10 pins, XLR connectors from different manufacturers will intermate, with the exception of Switchcraft six-pin models, which use a non-standard arrangement for the pins. Three-pin XLR connectors are by far the most common style, and are a standard for balanced audio signals. The great majority of microphones use the XLR connector. In previous years, they were used for connections, for instance by Trace Elliot in its bass enclosures. The XLR could accept 14 AWG wire with a capacity of 15 amps, suitable for most loudspeakers. The Speakon connector accepts larger wire and carries current, and it provides a better shield for the contacts. Three-pin XLR connectors are used to interconnect powered speakers with line-level signals and this use is commonly seen in PA system applications and seems to be growing more common
35.
DI box
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DIs are frequently used to connect an electric guitar or electric bass to a mixing consoles microphone input jack. The DI performs level matching, balancing, and either active buffering or passive impedance matching/impedance bridging to minimize unwanted noise, distortion, DI boxes are extensively used with professional and semi-professional PA systems, professional sound reinforcement systems and in sound recording studios. DI units are referred to as a DI box, direct box. The term is claimed to stand for direct input, direct injection. These boxes typically contained an audio transformer with a ratio from approximately 8,1 to 12,1. With this kind of transformer, the voltage of the instrument is stepped down to a range compatible with the typical mixing consoles microphone preamp. The typical console preamp input impedance of 1,500 ohms would appear to the instrument as a high input impedance of 216,000 ohms. To accommodate these instruments, active direct boxes were designed containing powered electronic circuitry which increased the input impedance from about 200,000 to above 1,000,000 ohms. In 1975, a 48-volt phantom powered active direct box was designed for Leon Russells recording studio, its published in dB. The direct box takes a high impedance, unbalanced signal and converts it to a low impedance, furthermore, the lower impedance allows an insignificant load to the input of a mixing console or preamp which is also designed to accept input from low impedance microphones. Because all cables using in live sound and recording are capacitive, using a DI box provides a balanced cable, which reduces radio frequency noise and electromagnetic problems coming from lighting systems. Mic cables are typically XLR cables, which are balanced cables, on the other hand, another advantage of DI units is that the DI contains a. balancing transformer that reduces ground‑loop problems and potential electrical safety issues under fault conditions. A passive DI unit typically consists of a transformer used as a balun. The term passive indicates that the unit does not require a battery or other source to operate. This makes passive DIs less expensive, but it means that they cannot include preamplifier features which enable the user to boost the gain. The turns ratio on a passive DI is typically chosen to convert a nominal 50 kΩ signal source to the 100–200 Ω expected by the mic input of an audio mixer, typical turns ratios are in the range of 10,1 to 20,1. Less commonly, a passive DI unit may consist of a resistive load, such units are best suited to outputs designed for headphones or loudspeakers. The less expensive passive DI units are more susceptible to hum, however, they require no batteries, are simpler to use, and the better units are extremely reliable when used as designed
36.
Phone connector (audio)
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A phone connector, also known as phone jack, audio jack, headphone jack or jack plug, is a common family of electrical connector typically used for analog signals, primarily audio. It is cylindrical in shape, typically two, three, four and, recently, five contacts. Three-contact versions are known as TRS connectors, where T stands for tip, R stands for ring, similarly, two-, four- and five- contact versions are called TS, TRRS and TRRRS connectors respectively. The phone connector was invented for use in telephone switchboards in the 19th century and is widely used. In its original configuration, the diameter of the sleeve conductor is 1⁄4 inch. The mini connector has a diameter of 3.5 mm, specific models are termed stereo plug, mini-stereo, mini jack, headphone jack and microphone jack, or are referred to by size, i. e.3. 5mm or 6. 35mm. In the UK, the terms jack plug and jack socket are commonly used for the male and female phone connectors. In the US, an electrical connector is called a jack. Phone plugs and jacks are not to be confused with the similar terms phono plug and phono jack which refer to RCA connectors common in consumer hi-fi, the 3.5 mm connector is, however, sometimes—but counter to the connector manufacturers nomenclature—referred to as mini phono. Modern phone connectors are available in three standard sizes, the original 1⁄4 in version dates from 1878, when it was used for manual telephone exchanges, making it the oldest electrical connector standard still in use. The 3.5 mm or miniature and 2.5 mm or sub-miniature sizes were originally designed as two-conductor connectors for earpieces on transistor radios since the 1950s, the standard still used today. The 3.5 mm connector, which is the most commonly used in application today, was popularized by the Sony EFM-117J radio which was released in 1964. It became very popular with its application on the Walkman in 1979, the 3.5 mm and 2.5 mm sizes are sometimes referred to as 1⁄8 in and 3⁄32 in respectively in the United States, though those dimensions are only approximations. All three sizes are now available in two-conductor and three-conductor versions. Four- and five-conductor versions of the 3.5 mm plug are used for certain applications, a four-conductor version is often used in compact camcorders and portable media players, and sometimes also in laptop computers and smartphones, providing stereo sound plus a video signal. Proprietary interfaces using both four- and five-conductor versions exist, where the conductors are used to supply power for accessories. The four-conductor 3.5 mm plug is used as a connector on handheld amateur radio transceivers from Yaesu. It is also used in some amps like the LH Labs Geek Out V2+ for a balanced output, the most common arrangement remains to have the male plug on the cable and the female socket mounted in a piece of equipment, the original intention of the design
37.
Line level
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Line level is the specified strength of an audio signal used to transmit analog sound between audio components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles. As opposed to line level, there are weaker audio signals, such as those from microphones and instrument pickups, the strength of these various signals does not necessarily refer to the output voltage of the source device, it also depends on its output impedance and output power capability. Consumer electronic devices concerned with audio often have a labeled line in and/or line out. Line out provides a signal output and line in receives a signal input. Professional equipment commonly uses balanced connections on 6.35 mm TRS phone jacks or XLR connectors, professional equipment may also use unbalanced connections with TS phone jacks. A line level describes a lines nominal signal level as a ratio, expressed in decibels, the nominal level and the reference voltage against which it is expressed depend on the line level being used. While the nominal levels themselves vary, only two reference voltages are common, decibel volts for consumer applications, and decibels unloaded for professional applications, the decibel volt reference voltage is 1 VRMS =0 dBV. The decibel unloaded reference voltage,0 dBu, is the AC voltage required to produce 1 mW of power across a 600 Ω impedance. This awkward unit is a holdover from the early telephone standards, which used 600 Ω sources and loads, modern audio equipment does not use 600 Ω matched loads, hence dBm unloaded. The most common nominal level for consumer audio equipment is −10 dBV, and the most common nominal level for professional equipment is +4 dBu. Expressed in absolute terms, a signal at −10 dBV is equivalent to a wave signal with a peak amplitude of approximately 0.447 volts. A signal at +4 dBu is equivalent to a wave signal with a peak amplitude of approximately 1.736 volts. Peak-to-peak amplitude refers to the voltage swing of a signal. For instance, a signal with an amplitude of ±0.5 V has a p-p amplitude of 1.0 V. The line level signal is a current signal without a DC offset. Instead, line level circuits use the impedance bridging principle, in which a low impedance output drives a high impedance input, a typical line out connection has an output impedance from 100 to 600 Ω, with lower values being more common in newer equipment. Line inputs present a higher impedance, typically 10 kΩ or more. Most of the voltage asserted by the output appears across the input impedance, the line input acts similarly to a high impedance voltmeter or oscilloscope input, measuring the voltage asserted by the output while drawing minimal current from the source
38.
RCA connector
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An RCA connector, sometimes called a phono connector or Cinch connector, is a type of electrical connector commonly used to carry audio and video signals. The connectors are sometimes casually referred to as A/V jacks. The name RCA derives from the Radio Corporation of America, which introduced the design by the early 1940s for internal connection of the pickup to the chassis in home radio-phonograph consoles. It was originally a low-cost, simple design, intended only for mating, refinement came with later designs, although they remained compatible. However, quarter-inch phone connectors are common in professional audio. The connections plug is called an RCA plug or phono plug, the name phono plug is sometimes confused with a phone plug which may refer to a quarter-inch phone plug – Tip/Sleeve or Tip/Ring/Sleeve connector – or to a 4P4C connector used for a telephone. In the most normal use, cables have a plug on each end, consisting of a central male connector. The ring is often segmented for flexibility, devices mount the socket, consisting of a central hole with a ring of metal around it. The ring is smaller in diameter and longer than the ring on the plug. The jack has an area between the outer and inner rings which is filled with an insulator, typically plastic. Its use as a connector for video signals is extremely common. RCA connectors and cable are commonly used to carry S/PDIF-formatted digital audio. Connections are made by pushing the cables plug into the jack on the device. Continuous noise can occur if the plug partially falls out of the jack, breaking ground connection, some variants of the plug, especially cheaper versions, also give very poor grip and contact between the ground sheaths due to their lack of flexibility. They are often color-coded, yellow for composite video, red for the audio channel. This trio of jacks can be found on the back of almost all audio, one or more sets are often found on TV sets to facilitate connection of camcorders, other portable video sources and video game consoles. Varying cable quality means that a cheap line-level audio cable might not successfully transfer component video, cables should meet the S/PDIF specification as defined by the international standard IEC 60958-3 for assured performance. The male plug has a pin which is 3.175 mm in diameter
39.
CD player
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A CD player is an electronic device that plays audio compact discs, which are a digital optical disc data storage format. CD players were first sold to consumers in 1982, CDs typically contain recordings of audio material such as music. CD players are often a part of home systems, car audio systems. With the exception of CD boomboxes, most CD players do not produce sound by themselves, most CD players only produce an output signal via a headphone jack and/or RCA jacks. To listen to using a CD player with a headphone output jack. To use a CD player in a stereo system, the user connects an RCA cable to the RCA jacks or other outputs and connects it to a hi-fi. They are also manufactured as portable devices, which are battery powered, modern units can play other formats in addition to PCM audio coding used in CDs, such as MP3, AAC and WMA. DJs playing dance music at clubs often use specialized players with a playback speed to alter the pitch. Audio engineers using CD players to play music for an event through a reinforcement system use professional audio-grade CD players. CD playback functionality is also valuable on CD-ROM/DVD-ROM drive equipped computers as well as on DVD players, American inventor James T. Russell has been credited with inventing the first system to record digital information on an optical transparent foil that is lit from behind by a high-power halogen lamp. Russells patent application was first filed in 1966, and he was granted a patent in 1970, following litigation, Sony and Philips licensed Russells patents in the 1980s. The Compact Disc is an evolution of LaserDisc technology, where a laser beam is used that enables the high information density required for high-quality digital audio signals. Prototypes were developed by Philips and Sony independently in the late 1970s, in 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the Red Book CD-DA standard was published in 1980, after their commercial release in 1982, compact discs and their players were extremely popular. Despite costing up to $1,000, over 400,000 CD players were sold in the United States between 1983 and 1984. The success of the disc has been credited to the cooperation between Philips and Sony, who came together to agree upon and develop compatible hardware. The unified design of the disc allowed consumers to purchase any disc or player from any company. In 1974, L. However, due to the performance of the analog format
40.
Clipping (audio)
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Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability. Driving an amplifier into clipping may cause it to power in excess of its power rating. As the signal simply cuts or clips at the capacity of the amplifier. The extra signal which is beyond the capability of the amplifier is simply cut off, many electric guitar players intentionally overdrive their guitar amplifiers to cause clipping and other distortion in order to get a desired sound. Amplifiers have voltage, current and thermal limits, clipping may occur due to limitations in the power supply or the output stage. Some amplifiers are able to peak power without clipping for short durations before energy stored in the power supply is depleted or the amplifier begins to overheat. This extra power can cause damage to components, including the woofer, tweeter, or crossover. In the frequency domain, clipping produces harmonics at higher frequencies than the unclipped signal and this additional high frequency energy has the potential to damage a loudspeaker via overheating. As a result, many designers have incorporated circuits to prevent clipping. Such circuits compare the signal to the output signal to detect the presence of extra power caused by distortion. The simplest circuits act like a fast limiter, which engages after about one decibel of clipping is detected, a more complex circuit, called soft-clip, was used from the 1980s onward to limit the signal at the input stage. The soft-clip feature begins to engage prior to clipping, for starting at 10 dB below maximum output power. The output waveform retains a rounded characteristic even in the presence of an input signal as much as 10 dB higher than maximum specified. In digital signal processing, clipping occurs when the signal is restricted by the range of a chosen representation, as seen on the oscilloscope, the wave resulting from the clipping is not a full sine wave. To avoid this, the level of a mix can be lowered. It is not simple to eliminate all clipping, as filtering can align various frequencies in such a way as to create excessive peak outputs, the excessive peaks may become clipped even though the amplifier can play any single sine wave without clipping. As such, some audiophiles will use amplifiers that are rated for power outputs over twice the speakers ratings and it is preferable to avoid clipping, but if a recording has clipped, and cannot be re-recorded, repair is an option. The goal of repair is to make up a replacement for the clipped part of the signal
41.
Mid-range speaker
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A mid-range speaker is a loudspeaker driver that reproduces sound in the frequency range from 250 to 2000 Hz. It is also known as a squawker, mid-range drivers are usually cone types or, less commonly, dome types, or compression horn drivers. Cone mid-range drivers typically resemble small woofers, the most common material used for mid-range cones is paper, occasionally impregnated and/or surface-treated with polymers or resins in order to improve vibrational damping. Most professional concert mid-range drivers are compression drivers coupled to horns, a very few mid-ranges are electrostatic drivers, planar magnetic drivers, or ribbon drivers. This region contains most sounds which are the most familiar to the ear. It is therefore paramount that a driver of good quality be capable of low-distortion reproduction. Most television sets and small radios have only a single mid-range driver, since, in the case of television the most important aspect is the talking, it works out well. Mid-range drivers are used in three way multi driver speaker systems. There are therefore special considerations involved in the join between the mid-range and both the low frequency and the high frequency drivers. The nature of the drivers on both sides of the mid-range, and the mid-range itself affect the selection of crossover frequency and slope. Nearly all crossovers are passive circuits, designed to match the characteristics of the drivers and their mounting, and are built of capacitors, inductors, active or electronic crossovers are used in some high performance hi-fi speakers, and in professional sound reinforcement systems. Grilles, especially those with structural frames, can modify the output of the entire speaker system. One of the used in design circles to describe some of these diffraction and reflection artifacts is the baffle step effect. Loudspeaker Loudspeaker enclosure Audio crossover Full-range speaker Tweeter Super tweeter Woofer Subwoofer
42.
Patch bay
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Patch panels are commonly used in computer networking, recording studios, radio and television. Patchbays make it easier to connect different devices in different orders for different projects and this means that devices mounted in racks or keyboard instruments can be connected without having to hunt around behind the rack or instrument with a flashlight for the right jack. Using a patchbay also saves wear and tear on the jacks of studio gear and instruments. Patch panels are being used more prevalently in domestic installations, owing to the popularity of Structured Wiring installs and they are also found in home cinema installations more and more. It is conventional to have the top row of jacks wired at the rear to outputs, patch bays may be half-normal or full-normal, normal indicating that the top and bottom jacks are connected internally. With top half-normal wiring, the same happens but vice versa, if a patch bay is wired to full-normal, then it includes break contacts in both rows of jacks. Dedicated switching equipment can be an alternative to patch bays in some applications, switches can make routing as easy as pushing a button, and can provide other benefits over patch bays, including routing a signal to any number of destinations simultaneously. However, switching equipment that can emulate the capabilities of a patch bay is much more expensive. There are various types of switches for audio and video, from simple selector switches to sophisticated production switchers, however, emulating or exceeding the capabilities of audio and/or video patch bays requires specialized devices like routing switches and crossbar switches. Switching equipment may be electronic, mechanical, or electro-mechanical, some switcher hardware can be controlled via computer and/or other external devices. Some have automated and/or pre-programmed operational capabilities, there are also software switcher applications used to route signals and control data within a pure digital computer environment. Distribution frames are cheaper, but less convenient, cable management Wiring closet This article incorporates public domain material from the General Services Administration document Federal Standard 1037C
43.
Electrical connector
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An electrical connector, is an electro-mechanical device used to join electrical terminations and create an electrical circuit. Electrical connectors consist of plugs and jacks, the connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices. An adapter can be used to bring together dissimilar connectors. There are hundreds of types of electrical connectors, connectors may join two lengths of flexible copper wire or cable, or connect a wire or cable to an electrical terminal. In computing, a connector can also be known as a physical interface. Cable glands, known as cable connectors in the US, connect wires to devices rather than electrically and are distinct from quick-disconnects performing the latter. It is usually desirable for a connector to be easy to visually, rapid to assemble, require only simple tooling. In some cases an equipment manufacturer might choose a connector specifically because it is not compatible with those other sources. No single connector has all the properties, the proliferation of types is a reflection of differing requirements. Fretting is a failure mode in electrical connectors that have not been specifically designed to prevent it. Many connectors are keyed, with some mechanical component which prevents mating except with a correctly oriented matching connector, some connector housings are designed with locking mechanisms to prevent inadvertent disconnection or poor environmental sealing. Locking mechanism designs include locking levers of various sorts, screw locking, a terminal is a simple type of electrical connector that connects two or more wires to a single connection point. Wire nuts are another type of single point connector, terminal blocks provide a convenient means of connecting individual electrical wires without a splice or physically joining the ends. They are usually used to connect wiring among various items of equipment within an enclosure or to make connections among individually enclosed items. Since terminal blocks are available for a wide range of wire sizes and terminal quantity. One type of terminal block accepts wires that are prepared only by removing a short length of insulation from the end, another type accepts wires that have ring or spade terminal lugs crimped onto the wires. Printed circuit board mounted terminal blocks allow individual wires to be connected to the circuit board, a general type of connector that simply screws or clamps bare wire to a post, such connectors are frequently used in electronic test equipment and audio. Many, but not all binding posts will also accept a banana connector plug, since stripping the insulation from wires is time-consuming, many connectors intended for rapid assembly use insulation-displacement connectors so that insulation need not be removed from the wire
44.
Noise gate
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A noise gate or gate is an electronic device or software that is used to control the volume of an audio signal. Comparable to a compressor, which attenuates signals above a threshold, however, noise gates attenuate signals by a fixed amount, known as the range. In its simplest form, a noise gate allows a signal to pass through only when it is above a set threshold, if the signal falls below the threshold, no signal is allowed to pass, the gate is closed. A noise gate is used when the level of the signal is above the level of the noise, the threshold is set above the level of the noise and so when there is no signal, the gate is closed. A noise gate does not remove noise from the signal, when the gate is open, both the signal and the noise will pass through. Gates typically feature attack, release, and hold settings and may feature a look-ahead function, noise gates have a Threshold control to set the level at which the gate will open. More advanced noise gates have more features, the Release control is used to define the length of time the gate takes to change from open to fully closed. A fast release abruptly cuts off the sound, whereas a slower release smoothly attenuates the signal from open to closed, if the release time is too short, a click can be heard when the gate re-opens. Release is the second-most common control to find on a gate, the Attack control is used to define the length of time the gate takes to change from closed to fully open. The Hold control is used to define the length of time the gate will stay open after the signal falls below the threshold. The hold control is set to ensure the gate does not close during short pauses between words or sentences in a speech signal. The Range control is used to set the amount of attenuation to be applied to the signal when the gate is closed, often there will be complete attenuation, that is no signal will pass when the gate is closed. In some circumstances, complete attenuation is not desired and the range can be changed, Advanced gates have an external sidechain. This is an input that allows the gate to be triggered by another audio signal. Noise gates often implement hysteresis, that is, they have two thresholds, one to open the gate and another, set a few dB below, a longer hold time also helps to avoid chattering, as described above. The basic function of a gate is to eliminate sounds below a given threshold. Noise gates are used in the recording studio and sound reinforcement. Rock musicians may use small portable units to control unwanted noise from their amplification systems
45.
Buffer amplifier
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Two main types of buffer exist, the voltage buffer and the current buffer. A voltage buffer amplifier is used to transfer a voltage from a first circuit, having an output impedance level. The interposed buffer amplifier prevents the circuit from loading the first circuit unacceptably. In the ideal voltage buffer in the diagram, the resistance is infinite. Other properties of the buffer are, perfect linearity, regardless of signal amplitudes. If the voltage is transferred unchanged, the amplifier is a unity gain buffer, although the voltage gain of a voltage buffer amplifier may be unity, it usually provides considerable current gain and thus power gain. However, it is commonplace to say that it has a gain of 1, as an example, consider a Thévenin source driving a resistor load RL. Because of voltage division the voltage across the load is only VA RL /, at the output the dependent voltage source delivers voltage Av VA = VA to the load, again without voltage division because the output resistance of the buffer is zero. A Thévenin equivalent circuit of the combined original Thévenin source and the buffer is a voltage source VA with zero Thévenin resistance. Typically a current buffer amplifier is used to transfer a current from a first circuit, having a low output impedance level, the interposed buffer amplifier prevents the second circuit from loading the first circuits current unacceptably and interfering with its desired operation. In the ideal current buffer in the diagram, the impedance is infinite. Again, other properties of the buffer are, perfect linearity, regardless of signal amplitudes. As an example, consider a Norton source driving a resistor load RL, because of current division the current delivered to the load is only IA RA /. However, if the Norton source drives a unity gain buffer such as that in Figure 1, at the output the dependent current source delivers current βi IA = IA to the load, again without current division because the output resistance of the buffer is infinite. A Norton equivalent circuit of the combined original Norton source and the buffer is a current source IA with infinite Norton resistance. Unity gain here implies a voltage gain of one, but significant current gain is expected, in this configuration, the entire output voltage is fed back into the inverting input. The difference between the input voltage and the inverting input voltage is amplified by the op-amp. This connection forces the op-amp to adjust its output voltage equal to the input voltage
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