807 (vacuum tube)
The 807 is a beam tetrode vacuum tube, widely used in audio- and radio-frequency power amplifier applications.
Audio uses
807s were used in audio power amplifiers, both for public address and hi-fi application, usually being run in push-pull pairs in class AB1 or AB2 giving up to 120 watts of usable power. The plate voltage limit is 750 volts and the screen grid limited to 300 volts. Because of the 300 volt screen grid voltage limit, the 807 cannot be triode connected for high power applications. Failure to observe this precaution will cause screen grid failure. Less commonly a single 807 was used in a pure class-A, single-ended audio output stage delivering about 10 watts.
The 807 is not a good choice of tube for typical Ultra-Linear amplifier circuits, as the maximum screen voltage at 300 V is less than half the maximum plate voltage of 750 V. A possible solution is to use an output transformer with a separate ultralinear screen winding, such as the Acrosound TO-350.
RF uses
Vacuum tube
In electronics, a vacuum tube, an electron tube, or just a tube (North America), or valve (Britain and some other regions) is a device that controls electric current between electrodes in an evacuated container. Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament. This type is called a thermionic tube or thermionic valve. A phototube, however, achieves electron emission through the photoelectric effect. Not all electronic circuit valves/electron tubes are vacuum tubes (evacuated); gas-filled tubes are similar devices containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases, usually without a heater.
The simplest vacuum tube, the diode, contains only a heater, a heated electron-emitting cathode (the filament itself acts as the cathode in some diodes), and a plate (anode). Current can only flow in one direction through the device between the two electrodes, as electrons emitted by the cathode travel through the tube and are collected by the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids. Tubes with grids can be used for many purposes, including amplification, rectification, switching, oscillation, and display.
Tube
Tube, or Tubes, may refer to:
Film, television, and Internet
Music
Construction and mechanics
Tube (band)
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Tube (チューブ, chūbu) is a Japanese pop rock band formed in 1985. The members of the group are Nobuteru Maeda (前田亘輝), Michiya Haruhata (春畑道哉) Hideyuki Kakuno (角野秀行) and Ryoji Matsumoto (松本玲二). Tube members Maeda and Haruhata have composed for other artists under the Pipeline Project alias. Since the group released most of its songs in April to July, the catchphrase originated "Summer comes with Tube".
Discography
Albums
Tube (container)
A tube is a soft squeezable container which can be used for thick liquids such as adhesive, caulking, ointment, and toothpaste. Basically, a tube is a cylindrical, hollow piece with a round or oval profile, made of plastic, paperboard, or aluminum. Both ends of this tube are treated differently during the manufacturing process and filling. In general, on one end of the tube body there is a round orifice, which can be closed by different caps and closures. The orifice can be shaped in many different ways. Plastic nozzles in various styles and lengths are just one good example.
To attach caps and closures, in most cases a thread is tapped onto the opening structure. Furthermore, something all aluminium tubes have in common is that the other open end is folded several times after the contents have been added. The tube is thus hermetically sealed and nearly germ-free due to the high temperatures during the production process. Furthermore, it is possible to coat the inside of the tube with special coatings to prevent the material from reacting with the contents.
Vacuum
Vacuum is space void of matter. The word stems from the Latin adjective vacuus for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is lower than atmospheric pressure. The Latin term in vacuo is used to describe an object as being in what would otherwise be a vacuum.
The quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. Much higher-quality vacuums are possible. Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth (10−12) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm3.Outer space is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average. According to modern understanding, even if all matter could be removed from a volume, it would still not be "empty" due to vacuum fluctuations, dark energy, transiting gamma rays, cosmic rays, neutrinos, and other phenomena in quantum physics. In the electromagnetism in the 19th century, vacuum was thought to be filled with a medium called aether. In modern particle physics, the vacuum state is considered the ground state of matter.
Vacuum (disambiguation)
Vacuum is the absence of matter.
Vacuum may also refer to:
Podcasts:
