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Topic: Thermionic valve

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In the News (Sun 23 Jun 19)

 Patent Specification No. 474,607
The anode of this valve is connected through a resistance to the positive terminal of the source of supply and a condenser and leak resistance having a time constant of the same order as that of the preceding coupling, serve to couple the anode to the grid of a second triode valve.
The anode of the triode valve 21 is connected through a resistance 28 to the positive terminal 2 of the source of supply and a connection is taken from the end of this resistance nearest the anode, through two decoupling resistances 29 and 30 in series to the grid of a triode valve 31.
A circuit arrangement according to Claim 3 wherein a third thermionic valve is inserted between the anode of the second valve and the grid of the regulating valve, the grid of the regulating valve being connected directly to the cathode of the third valve.
www.doramusic.com /patents/474607.htm   (3215 words)

 Patent Specification No. 496,083
It is the chief object of the present invention to provide an improved circuit in which the characteristic impedance of valves of the kind referred to can be more nearly matched to their optimum loads and in which the danger of an excessive increase of voltage on removal of the load may be substantially avoided.
According to the invention a thermionic valve amplifying circuit is provided employing a pentrode or tetrode valve in which the screening grid of the valve is so connected that the potential thereof varies in proportion to the A.C. potential variations of the anode of the valve.
Valves of this kind give a greater output for a given anode potential than triodes, but they suffer from the disadvantage that their internal impedance is very much greater than the ratio of the steady D.C. voltage to the steady D.C. current.
www.doramusic.com /patents/496883.htm   (2101 words)

 The Audio Circuit, information, schematics and manuals   (Site not responding. Last check: 2007-10-21)
The invention of the vacuum tube or thermionic valve brought the dawn of the age of electronics.
Valves or tubes were difficult and expensive to make and their heaters consumed large amounts of power and this had to be supplied by expensive batteries.
Not only were thermionic valves used in radios which by this time were very popular, but they also found many other uses.
www.audiocircuit.com /A-HTML/AA-General-GEN/920-GEN-HIS-VAC_____-O-A01.htm   (2179 words)

 Highbeam Encyclopedia - Search Results for thermionic
The number of thermions emitted increases rapidly as the temperature of the substance rises.
He was a leader in the development of electric lighting, the telephone, and wireless telegraphy in England and the inventor of a thermionic valve (the first electron tube).
Fleming's valve was a rectifier, or diode, consisting of two electrodes in an evacuated glass envelope.
www.encyclopedia.com /searchpool.asp?target=thermionic   (626 words)

 Vacuum tube - Encyclopedia.WorldSearch   (Site not responding. Last check: 2007-10-21)
In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal.
The valve equivalent of a transistor, triodes were used in early valve amplifiers.
This distortion was an undesirable distortion at low volume, not to be confused with the desirable distortion that tube amplifiers exhibit at high volume levels (the latter known as the valve sound).
encyclopedia.worldsearch.com /thermionic_valve.htm   (3129 words)

 Fleming   (Site not responding. Last check: 2007-10-21)
His work with the thermionic valve in 1904 and 1905 was important to the development of radio.
He observed that the direct current which passed through the valve was related to the amount of radio frequency power applied to it and hence was born the rectifier principle which is still the basis of the whole electronics industry - even today.
Really the valve could scarcely be considered as a very versatile device at all until the grid was introduced because there was no means of controlling the current flowing in the valve other than by varying the amount of power supplied between the filament and the anode.
chem.ch.huji.ac.il /~eugeniik/history/fleming.htm   (3286 words)

 Radio-Electronics.Com :: Vacuum Tube Basic Introduction
Thermionic valves or vacuum tubes come in many forms including the diode, triode, tetrode, pentode, heptode and many more.
However the most widely used thermionic device today is the cathode ray tube that is still manufactured by the million for use in television sets, computer monitors, oscilloscopes and a variety of other electronic equipment.
Later this was discovered that this was not the case and new "hard" valves were made that had a superior performance to the older "soft" valves.
www.radio-electronics.com /info/data/valve/valve_theory/tube_basic_theory.php   (1114 words)

 Thermionic Culture Valve Designs   (Site not responding. Last check: 2007-10-21)
To this end, Thermionic Culture was founded in 1999 by Vic and Jon Bailes, a designer in the electronic manufacturing industry.
Some of the Thermionic Culture circuit topologies and concepts can be traced back to the classic valve designs from the 1940s, but a lot of the detailed designs involve Vic's own innovative work.
Regardless of the source of inspiration, all of the valve circuitry has been revised and optimised to achieve the performance, low noise levels and minimal distortion expected of modern recording equipment.
www.soundonsound.com /sos/jun04/articles/vickeary.htm   (2415 words)

 Vacuum tube - Wikipedia, the free encyclopedia
In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space.
Vacuum tubes, or thermionic valves, are arrangements of electrodes in a vacuum within an insulating, temperature-resistant envelope.
The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air.
en.wikipedia.org /wiki/Vacuum_tube   (3298 words)

 Thermionic Valves - Theory
The characteristics of the thermionic diode are shown in Figure 02.
The use of the thermionic diode is thus restricted to its linear region AB.
Some valves have more than one grid and numerical subscripts are used, as ec1, ec2, With the grid nearest the cathode considered grid 1.
www.livinginthepast.demon.co.uk /vtheory/vtheory.htm   (3854 words)

 thermionic emission - Encyclopedia.com
thermionic emission, emission of electrons or ions by substances that are highly heated, the charged particles being called thermions.
The heated material may be in the form of a metal filament or of some compound that coats and is heated by the filament.
Thermionic emission's most important practical application in electronics is in the electron tube, since it is the mechanism by which electrons are emitted from the cathode.
www.encyclopedia.com /doc/1E1-thermion.html   (384 words)

Another antique is a Sean Davies valve limiter made in the 1960's for IBC studios where Keary claims it was used on early Who tracks such as My Generation.
Some of the valves in the desk should be replaced every 18 months or so, but an input valve like an EF86 will go on for years - I've actually got some in the desk that are 20 years old and still going strong.
It's a peculiar design in that the record electronics are valve, while the reply and motor amps are transistor and sound bloody awful.
www.thermionicculture.com /mrthermionic/index.htm   (2232 words)

 Introduction to Thermionic Valves
The diode valve is basically little more than an electric light bulb (in the form of a wire filament heated by an electric current) with the addition of a metal plate, known as the anode.
Although this illustration describes "Amplified impulses passing to loud-speaker", in practice a transformer is required between the valve anode circuit and a loudspeaker, as the valve anode circuit is high impedance (high voltage, low current), whereas a loudspeaker is low impedance, requiring high current at low voltage.
A well designed tetrode valve has a Cga which is reduced by a factor of several hundred to 1000 compared with a triode, and the gain is increased from about 15 to about 40.
www.cjseymour.plus.com /elec/valves/valves.htm   (6829 words)

 Marshall Amps :: The Secret Life Of Valves
The term 'valve' is purely the shortened form of 'thermionic valve' Now, although we Brits call 'em valves, our transatlantic cousins in America prefer to call 'em 'tubes'.
This seemingly simple addition gave versatility to the valve because by varying the potential [voltage] connected to the grid, the flow of electrons could be increased or decreased.
The type of valves used in all Marshall pre-amp stages is the double triode ECC83 or 12AX7 [ECC83 is the English name for this valve, 12AX7 is the American - further proof that we are two countries separated by a common language!].
www.marshallamps.com /resources/secret_life_of_valves/secret_life_valves.asp   (1861 words)

 Vacuum Tube | World of Invention
The invention of the vacuum tube (or valve, as it is known in Britain) led to the electronic revolution.
Fleming called his device the thermionic valve because it used heat to control the flow of electricity just as a valve controls the flow of water.
Fleming's thermionic valve operated at a temperature of 4500° F (2500° C), generating a considerable amount of heat.
www.bookrags.com /research/vacuum-tube-woi   (713 words)

 John Ambrose Fleming - Wikipedia, the free encyclopedia
In November 1904 he invented and patented the two-electrode radio rectifier, which he called the oscillation valve.
It was also called a thermionic valve, vacuum diode, kenotron, thermionic tube, or Fleming valve.
In 1906 Lee De Forest of the USA added a control grid to the valve to create a vacuum tube RF detector called the Audion, leading Fleming to accuse him of plagiarism.
en.wikipedia.org /wiki/John_Ambrose_Fleming   (263 words)

 Adventures in CyberSound
In later modern valves the tungsten was coated with an oxide (such as barium or strontium) which gives good emission at around 700 deg C. In most valves the emitting conductor is a separate component to the heating filament.
The valve electrodes are indicated by the normal abbreviations - a for anode, k for cathode and h for the heater connections.
The purpose of the transformer is to convert the relatively high anode impedance of the valve to the low impedance of the speaker.
www.acmi.net.au /AIC/VALVES_WORK.html   (1728 words)

 Valve Amplifiers
This is used in valved amplifiers to match the valves (which demand a high impedance load) to the loudspeaker, which is a low impedance device.
Valves deteriorate at a fairly steady rate, and regular replacement is essential for top performance to be maintained.
In our experience, a top valved amp gives a sweeter, smoother result than a top transistorised amp, but this is a generalisation and we have heard at least one transistorised amplifier, currently being developed by A~~, a local manufacturer, which seems to have none of the audible deficiencies of either type.
sound.westhost.com /hfr_be.htm   (2498 words)

 Learn more about Vacuum tube in the online encyclopedia.   (Site not responding. Last check: 2007-10-21)
For most purposes, the vacuum tube has been replaced by the much smaller and less expensive transistor, either as a discrete device or in an integrated circuit.
The non-linear operating characteristic of the triode gave early valve audio amplifiers a distortion that became known as the valve sound.
The valves are the two glass columns with the dark tops.
www.onlineencyclopedia.org /v/va/vacuum_tube.html   (1946 words)

 John Tiley
These valves were also essential components of all radio receivers at that time, including, of course, domestic wireless sets and so were commonly known as "wireless valves".
Today, nobody much under the age of sixty has ever seen a thermionic valve ; it was like a small electric light bulb emitting little light but a certain amount of heat.
Woe betide you if a valve failed in your wireless set, which was a not infrequent occurrence, because they were quite expensive items to replace.
members.aol.com /tiley7/page_17.htm   (1140 words)

 Thermionic Culture
In this day and age of mass-produced solid-state audio equipment it's a refreshing change for a company to constantly strive for the ultimate all valve signal path.
Some of the circuits take ideas from the 1940's to '60s and refine and update them to produce the low noise and distortion which are expected now.
Also, they select and match (where necessary) all of the valves that they supply so a far longer life span can be expected.
www.mercenary.com /thermionic.html   (341 words)

 Sir John Ambrose Fleming   (Site not responding. Last check: 2007-10-21)
Sir John Ambrose Fleming's invention of the thermionic valve (tube) jumpstarted modern electronics.
The two-electrode radio rectifier, which he called the thermionic valve; also known as the vacuum diode, kenotron, thermionic tube and Fleming valve was patented in 1904.
"Valves" were expensive to make, and in less than two years, the "cat's whisker" was produced, a crude form of semiconductor rectifier that consisted of a thin wire positioned on a lump of suitable material (even coal) to produce a point contact rectifier.
www.ce.org /Events/Awards/435.htm   (505 words)

 Thermionic Culture Culture Vulture
Thermionic Culture, a specialist British manufacturer of valve-based audio equipment, can trace its pedigree back to the 1950s, when the company's founder, Vic Keary, built his first studio.
The 'distortion' valve's configuration, bias and drive can all be adjusted to provide three different distortion modes, enabling second and/or third harmonic distortion, and with an amount variable from about 0.2 percent to 150 percent.
This machine is hand built in the traditional way, with full-size components strung between tag-strips in the lower section, and the valves, big reservoir capacitors and mains transformer mounted in the top section under a perforated lid.
www.soundonsound.com /sos/aug03/articles/culturevulture.htm   (1786 words)

 The Alan Blumlein Homepage
Blumlein developed the principle of defined current circuits in which the valve's current was defined either by a cathode resistance to a considerably lower potential, or by employing negative feedback.
This principle can be extended by having two valves (triodes or pentodes) working side by side, with their cathodes connected together and sharing the current from one long-tail resistor.
As a consequence the cathode current has to be limited to about a quarter of the valve's normal current, and the anode load resistance has to be increased by a factor of four to achieve the same output signal size.
www.alanturing.net /turing_archive/pages/blumlein   (2349 words)

 Page Title
The thermionic valve is normally operated with its anode current considerably less than the maximum emission produced by its cathode.
".....Under normal conditions a valve should be operated with its filament or heater at the recommended voltage ; in the case of an oxide coated valve it is possible to have fluctuations of the order of 10% up or down without seriously affecting the life or characteristics of the valve...
"During the working life of the valve, its emission usually increases over the early period, reaches a maximum at an age which varies from valve to valve and one manufacturer to another, and then begins to fall.
www.tubecad.com /october2000/page26.html   (555 words)

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