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David Hafler
David Hafler (February 7, 1919 – May 25, 2003) was an American audio engineer. He was best known for his work on an improved version of the Williamson amplifier using the ultra-linear circuit of Alan Blumlein. Biography In 1950, Hafler founded Acrosound with his colleague Herbert Keroes. This company was primarily in the business of designing and manufacturing transformers for tube amplifiers. Around this time Hafler and Keroes popularized the ultra-linear output-stage for audio amplifiers. However, the partnership did not last. In 1954 Hafler founded Dynaco with Ed Laurent. Hafler was instrumental in bringing affordable, high-quality audio kits to hobbyists, making his name a household word in the US audio community for many years. In the 1970s Hafler promoted "passive pseudo-quadraphonics", an inexpensive method of recreating ambient sounds at the rear from ordinary stereophonic recordings. Known as the "Hafler hookup" or " Hafler circuit", this consisted of two simila ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Philadelphia
West Philadelphia, nicknamed West Philly, is a section of the city of Philadelphia. Alhough there are no officially defined boundaries, it is generally considered to reach from the western shore of the Schuylkill River, to City Avenue to the northwest, Cobbs Creek to the southwest, and the SEPTA Media/Wawa Line to the south. An alternate definition includes all city land west of the Schuylkill; this would also include Southwest Philadelphia and its neighborhoods. The eastern side of West Philadelphia is also known as University City. Topography The topography of West Philadelphia is composed of rolling hills rising slowly from the Schuylkill River toward Cobbs Creek in the west and toward Belmont Plateau in the northwest. This gradual elevation makes the skyline of Center City visible from many points in West Philadelphia. The Wynnefield neighborhood is a location frequently used by photographers and organizers of civic events. Demographics According to the 2010 census, 216,4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decibel
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 101/10 (approximately ) or root-power ratio of 10 (approximately ). The unit expresses a relative change or an absolute value. In the latter case, the numeric value expresses the ratio of a value to a fixed reference value; when used in this way, the unit symbol is often suffixed with letter codes that indicate the reference value. For example, for the reference value of 1 volt, a common suffix is " V" (e.g., "20 dBV"). Two principal types of scaling of the decibel are in common use. When expressing a power ratio, it is defined as ten times the logarithm in base 10. That is, a change in ''power'' by a factor of 10 corresponds to a 10 dB change in level. When expressing root-power quantities, a change in ''ampl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2003 Deaths
3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious or cultural significance in many societies. Evolution of the Arabic digit The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and Chinese numerals) that are still in use. That was also the original representation of 3 in the Brahmic (Indian) numerical notation, its earliest forms aligned vertically. However, during the Gupta Empire the sign was modified by the addition of a curve on each line. The Nāgarī script rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a with an additional stroke at the bottom: ३. The Indian digits spread to the Caliphate in the 9th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1919 Births
Events January * January 1 ** The Czechoslovak Legions occupy much of the self-proclaimed "free city" of Pressburg (now Bratislava), enforcing its incorporation into the new republic of Czechoslovakia. ** HMY ''Iolaire'' sinks off the coast of the Hebrides; 201 people, mostly servicemen returning home to Lewis and Harris, are killed. * January 2– 22 – Russian Civil War: The Red Army's Caspian-Caucasian Front begins the Northern Caucasus Operation against the White Army, but fails to make progress. * January 3 – The Faisal–Weizmann Agreement is signed by Emir Faisal (representing the Arab Kingdom of Hejaz) and Zionist leader Chaim Weizmann, for Arab–Jewish cooperation in the development of a Jewish homeland in Palestine, and an Arab nation in a large part of the Middle East. * January 5 – In Germany: ** Spartacist uprising in Berlin: The Marxist Spartacus League, with the newly formed Communist Party of Germany and the Independent Social De ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereophile
''Stereophile'' is a monthly American audiophile magazine which reviews high-end audio equipment, such as loudspeakers and amplifiers, and audio-related news. History Founded in 1962 by J. Gordon Holt. ''Stereophile'' is the highest-circulation hi-fi magazine in the Americas and possibly the world. In 1998, ''Stereophile'' was acquired by Petersen Publishing. Until 2018, ''Stereophile'' was published in New York by The Enthusiast Network, a publisher of special interest magazines. The magazine was formerly based in Santa Fe, New Mexico Santa Fe ( ; , Spanish for 'Holy Faith'; tew, Oghá P'o'oge, Tewa for 'white shell water place'; tiw, Hulp'ó'ona, label=Tiwa language, Northern Tiwa; nv, Yootó, Navajo for 'bead + water place') is the capital of the U.S. state of New Mexico. .... During this period it was published eight times a year. until the August 1987 issue, when it started monthly publication. In March 2018, ''Stereophile'' was purchased, along with related magazine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Philadelphia Inquirer
''The Philadelphia Inquirer'' is a daily newspaper headquartered in Philadelphia, Pennsylvania. The newspaper's circulation is the largest in both the U.S. state of Pennsylvania and the Delaware Valley metropolitan region of Southeastern Pennsylvania, South Jersey, Delaware, and the northern Eastern Shore of Maryland, and the 17th largest in the United States as of 2017. Founded on June 1, 1829 as ''The Pennsylvania Inquirer'', the newspaper is the third longest continuously operating daily newspaper in the nation. It has won 20 Pulitzer Prizes . ''The Inquirer'' first became a major newspaper during the American Civil War. The paper's circulation dropped after the Civil War's conclusion but then rose again by the end of the 19th century. Originally supportive of the Democratic Party, ''The Inquirers political orientation eventually shifted toward the Whig Party and then the Republican Party before officially becoming politically independent in the middle of the 20th cen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parkinson's Disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms become more common. The most obvious early symptoms are tremor, rigidity, slowness of movement, and difficulty with walking. Cognitive and behavioral problems may also occur with depression, anxiety, and apathy occurring in many people with PD. Parkinson's disease dementia becomes common in the advanced stages of the disease. Those with Parkinson's can also have problems with their sleep and sensory systems. The motor symptoms of the disease result from the death of cells in the substantia nigra, a region of the midbrain, leading to a dopamine deficit. The cause of this cell death is poorly understood, but involves the build-up of misfolded proteins into Lewy bodies in the neurons. Collectively, the main motor symptoms are also known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Runaway
Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. It is a kind of uncontrolled positive feedback. In chemistry (and chemical engineering), thermal runaway is associated with strongly exothermic reactions that are accelerated by temperature rise. In electrical engineering, thermal runaway is typically associated with increased current flow and power dissipation. Thermal runaway can occur in civil engineering, notably when the heat released by large amounts of curing concrete is not controlled. In astrophysics, runaway nuclear fusion reactions in stars can lead to nova and several types of supernova explosions, and also occur as a less dramatic event in the normal evolution of solar-mass stars, the " he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOSFET
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. A metal-insulator-semiconductor field-effect transistor (MISFET) is a term almost synonymous with MOSFET. Another synonym is IGFET for insulated-gate field-effect transistor. The basic principle of the field-effect transistor was first patented by Julius Edgar Lilienfeld in 1925.Lilienfeld, Julius Edgar (1926-10-08) "Method and apparatus for controlling electric currents" upright=1.6, Two power MOSFETs in V_in_the_''off''_state,_and_can_conduct_a_continuous_current_of_30 surface-mount_packages._Operating_as_switches,_each_of_these_components_can_su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pennsauken, New Jersey
Pennsauken Township is a township in Camden County in the U.S. state of New Jersey. It is a suburb of Philadelphia. As of the 2020 U.S. census, the township's population was 37,074, reflecting an increase of 1,189 (+3.3%) from the 35,885 counted in the 2010 census. The township is part of the South Jersey region of the state. History Pennsauken Township was incorporated as a township by an act of the New Jersey Legislature on February 18, 1892, from portions of the now-defunct Stockton Township.Snyder, John P''The Story of New Jersey's Civil Boundaries: 1606-1968'' Bureau of Geology and Topography; Trenton, New Jersey; 1969. p. 108. Accessed July 24, 2012. The exact origin of the name Pennsauken is unclear, but it probably derives from the language of the Lenni Lenape Native Americans, who once occupied the area from "", the Lenape language term for tobacco pouch. Alternatively, the "Penn" in the township's name refers to William Penn, while "sauk" is a water inlet or outl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microphone
A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers for recording voice, speech recognition, VoIP, and for other purposes such as ultrasonic sensors or knock sensors. Several types of microphone are used today, which employ different methods to convert the air pressure variations of a sound wave to an electrical signal. The most common are the dynamic microphone, which uses a coil of wire suspended in a magnetic field; the condenser microphone, which uses the vibrating diaphragm as a capacitor plate; and the contact microphone, which uses a crystal of piezoelectric material. Microphones typically n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matrix Decoder
Matrix decoding is an audio technology where a small number of discrete audio channels (e.g., 2) are decoded into a larger number of channels on play back (e.g., 5). The channels are generally, but not always, arranged for transmission or recording by an encoder, and decoded for playback by a decoder. The function is to allow multichannel audio, such as quadraphonic sound or surround sound to be encoded in a stereo signal, and thus played back as stereo on stereo equipment, and as surround on surround equipment – this is "compatible" multichannel audio. Process Matrix encoding does ''not'' allow one to encode several channels in ''fewer'' channels without losing information: one cannot fit 5 channels into 2 (or even 3 into 2) without losing information, as this loses dimensions: the decoded signals are not independent. The idea is rather to encode something that will both be an acceptable approximation of the surround sound when decoded, and acceptable (or even superior) stereo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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