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Blackmer Gain Cell
The Blackmer gain cell is an audio frequency voltage-controlled amplifier (VCA) circuit with an exponential control law. It was invented and patented by David E. Blackmer between 1970 and 1973. The four-transistor core of the original Blackmer cell contains two complementary bipolar current mirrors that perform log-antilog operations on input voltages in a push-pull, alternating fashion. Earlier log-antilog modulators using the fundamental exponential characteristic of a p–n junction were unipolar; Blackmer's application of push-pull signal processing allowed modulation of bipolar voltages and bidirectional currents. The Blackmer cell, which has been manufactured since 1973, is the first precision VCA circuit that was suitable for professional audio. As early as the 1970s, production Blackmer cells achieved control range with total harmonic distortion of no more than 0.01% and very high compliance with ideal exponential control law. The circuit was used in remote-controlled ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Frequency
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch. The generally accepted standard hearing range for humans is 20 to 20,000 Hz. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. High frequencies are the first to be affected by hearing loss due to age or prolonged exposure to very loud noises. Sound frequencies above 20 kHz are called ultrasonic. Frequencies and descriptions See also *Absolute threshold of hearing *Hypersonic effect, controversial claim for human perception above 20,000 Hz *Loudspeaker *Musical acoustics *Piano key frequencies *Scientific pitch notation *Whistle register The whistle register (also called the flute regi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universal Audio
United Recording Electronics Industries (UREI) was a manufacturer of recording, mixing and audio signal processing hardware for the professional recording studio, live sound and broadcasting fields. History Bill Putnam Sr. founded Universal Audio in Chicago in the 1950s as a design and manufacturing addition to his recording studio business, Universal Recording Corporation. After Putnam moved to Hollywood in 1957 and established the United Recording Corporation, his company acquired Studio Supply Co. and rebranded it as the Studio Electronics Corporation (SEC) and moved all manufacturing to the second floor of Western Recorders. By December, 1965, Universal Audio had been completely absorbed by Studio Electronics, although Studio Electronics continued to produce some Universal Audio-branded products. In 1967, Studio Electronics acquired the broadcast division of Babcock Electronics, including Teletronix and the patent rights to the electro-optical LA-2A leveling amplifier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dolby B
A Dolby noise-reduction system, or Dolby NR, is one of a series of noise reduction systems developed by Dolby Laboratories for use in analog audio tape recording. The first was '' Dolby A'', a professional broadband noise reduction system for recording studios in 1965, but the best-known is '' Dolby B'' (introduced in 1968), a sliding band system for the consumer market, which helped make high fidelity practical on cassette tapes, which used a relatively noisy tape size and speed. It is common on high-fidelity stereo tape players and recorders to the present day, although Dolby has as of 2016 ceased licensing the technology for new cassette decks. Of the noise reduction systems, ''Dolby A'' and '' Dolby SR'' were developed for professional use. ''Dolby B'', '' C'', and '' S'' were designed for the consumer market. Aside from Dolby HX, all the Dolby variants work by companding: compressing the dynamic range of the sound during recording, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dolby A
A Dolby noise-reduction system, or Dolby NR, is one of a series of noise reduction systems developed by Dolby Laboratories for use in analog audio tape recording. The first was '' Dolby A'', a professional broadband noise reduction system for recording studios in 1965, but the best-known is '' Dolby B'' (introduced in 1968), a sliding band system for the consumer market, which helped make high fidelity practical on cassette tapes, which used a relatively noisy tape size and speed. It is common on high-fidelity stereo tape players and recorders to the present day, although Dolby has as of 2016 ceased licensing the technology for new cassette decks. Of the noise reduction systems, ''Dolby A'' and '' Dolby SR'' were developed for professional use. ''Dolby B'', '' C'', and '' S'' were designed for the consumer market. Aside from Dolby HX, all the Dolby variants work by companding: compressing the dynamic range of the sound during recording, and ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
State Of The Art
The state of the art (sometimes cutting edge or leading edge) refers to the highest level of general development, as of a device, technique, or scientific field achieved at a particular time. However, in some contexts it can also refer to a level of development reached at any particular time as a result of the common methodologies employed at the time. The term has been used since 1910, and has become both a common term in advertising and marketing, and a legally significant phrase with respect to both patent law and tort liability. In advertising, the phrase is often used to convey that a product is made with the best or latest available technology, but it has been noted that "the term 'state of the art' requires little proof on the part of advertisers", as it is considered mere puffery. The use of the term in patent law "does not connote even superiority, let alone the superlative quality the ad writers would have us ascribe to the term". Origin and history The origin of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JFET
The junction-gate field-effect transistor (JFET) is one of the simplest types of field-effect transistor. JFETs are three-terminal semiconductor devices that can be used as electronically controlled switches or resistors, or to build amplifiers. Unlike bipolar junction transistors, JFETs are exclusively voltage-controlled in that they do not need a biasing current. Electric charge flows through a semiconducting channel between ''source'' and ''drain'' terminals. By applying a reverse bias voltage to a ''gate'' terminal, the channel is ''pinched'', so that the electric current is impeded or switched off completely. A JFET is usually conducting when there is zero voltage between its gate and source terminals. If a potential difference of the proper polarity is applied between its gate and source terminals, the JFET will be more resistive to current flow, which means less current would flow in the channel between the source and drain terminals. JFETs are sometimes referred to as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the voltage or current (power, voltage or current amplifier). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a greater amplitude signal at its output. The ratio of output to input voltage, current, or power is termed gain (voltage, current, or power gain). An amplifier, by definition has gain greater than unity (if the gain is less than unity, the device is an attenuator). An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attenuator (electronics)
An attenuator is an electronic device that reduces the power of a signal without appreciably distorting its waveform. An attenuator is effectively the opposite of an amplifier, though the two work by different methods. While an amplifier provides gain, an attenuator provides loss, or gain less than 1. Construction and usage Attenuators are usually passive devices made from simple voltage divider networks. Switching between different resistances forms adjustable stepped attenuators and continuously adjustable ones using potentiometers. For higher frequencies precisely matched low VSWR resistance networks are used. Fixed attenuators in circuits are used to lower voltage, dissipate power, and to improve impedance matching. In measuring signals, attenuator pads or adapters are used to lower the amplitude of the signal a known amount to enable measurements, or to protect the measuring device from signal levels that might damage it. Attenuators are also used to 'match' impedance b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mix Automation
In music recording, mix automation allows the mixing console to remember the audio engineer's adjustment of faders during the post-production editing process. A timecode is necessary for the synchronization of automation. Modern mixing consoles and digital audio workstations use comprehensive mix automation. The need for mix automation originates from the 1970s and the changeover from studios mostly using eight-track tape machines to multiple, synchronized 24-track recorders. Mixing could be laborious and require up to four people, and the results could be almost impossible to reproduce. Manufacturers such as Solid State Logic and AMS Neve developed systems that enabled one engineer to oversee every detail of a complex mix, although the computers required to power these desks remained a rarity into the late 1970s. According to record producer Roy Thomas Baker, Queen's 1975 single "Bohemian Rhapsody" was one of the first mixes to be done with automation. Types ;Voltage Contr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise Reduction
Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an undesired signal component from the desired signal component, as with common-mode rejection ratio. All signal processing devices, both analog and digital, have traits that make them susceptible to noise. Noise can be random with an even frequency distribution (white noise), or frequency-dependent noise introduced by a device's mechanism or signal processing algorithms. In electronic systems, a major type of noise is ''hiss'' created by random electron motion due to thermal agitation. These agitated electrons rapidly add and subtract from the output signal and thus create detectable noise. In the case of photographic film and magnetic tape, noise (both visible and audible) is introduced due to the grain structure of the medium. In photograp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Master Tape
Mastering, a form of audio post production, is the process of preparing and transferring recorded audio from a source containing the Audio mixing (recorded music), final mix to a data storage device (the master), the source from which all copies will be produced (via methods such as pressing, duplication or Replication (optical media), replication). In recent years digital masters have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering. Mastering requires critical listening; however, software tools exist to facilitate the process. Results depend upon the intent of the engineer, the skills of the engineer, the accuracy of the speaker monitors, and the listening environment. Mastering engineers often apply Equalization (audio), equalization and dynamic range compression in order to optimize sound translation on all playback systems. It is standard pra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal-to-noise Ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR, bandwidth, and channel capacity of a communication channel are connected by the Shannon–Hartley theorem. Definition Signal-to-noise ratio is defined as the ratio of the power of a signal (meaningful input) to the power of background noise (meaningless or unwanted input): : \mathrm = \frac, where is average power. Both signal and noise power must be measured at the same or equivalent points in a system, and within the same system bandwidth. Depending on whether the signal is a constant () or a random variable (), the signal-to-noise ratio for random noise becomes: : \mathrm = \frac where E refers to the expected value, i.e. in this case ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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