Pentagrid amplifier classes

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Content:

• The 'All American Five'
• transistor frequency converter
• An Elementary Superregenerative Circuit
• List of vacuum tubes
• Vacuum Tubes
• Roy J. Tellason's Web Pages
• ゆうパケットまたは普通郵便 【購入金額15000円以上は宅配便】 BREED ブリード BULL TERRIER（ブルテリア）80gピンク金
• 6CS6 Pentagrid Class A Amplifier Miniature RCA Radiotron Electron Vacuum Tube

WATCH RELATED VIDEO: Class AB Audio Amplifier

The 'All American Five'

Click here to order virtually any vacuum tube you might need. Back in , British scientist John Ambrose Fleming first showed his device to convert an alternating current signal into direct current. The "Fleming diode" was based on an effect that Thomas Edison had first discovered in , and had not put to useful work at the time. This diode essentially consisted of an incandescent light bulb with an extra electrode inside.

When the bulb's filament is heated white-hot, electrons are boiled off its surface and into the vacuum inside the bulb. If the extra electrode also called an "plate" or "anode" is made more positive than the hot filament, a direct current flows through the vacuum. And since the extra electrode is cold and the filament is hot, this current can only flow from the filament to the electrode, not the other way. So, AC signals can be converted into DC. Fleming's diode was first used as a sensitive detector of the weak signals produced by the new wireless telegraph.

Later and to this day , the diode vacuum tube was used to convert AC into DC in power supplies for electronic equipment. Many other inventors tried to improve the Fleming diode, most without success. The only one who succeeded was New York inventor Lee de Forest.

In he patented a bulb with the same contents as the Fleming diode, except for an added electrode. This "grid" was a bent wire between the plate and filament. In fact, the grid was changing "modulating" the current flowing from the filament to the plate.

This device, the Audion, was the first successful electronic amplifier. It was the genesis of today's huge electronics industry. Between and the s, a staggering array of different tube families was developed, most derived from de Forest's invention. With a very few exceptions, most of the tube types in use today were developed in the s or s. One obvious exception is the B triode, which was first introduced by Western Electric in Svetlana's SVB version, plus many other brands, continue to be very popular with audiophiles around the world.

Various tubes were developed for radio, television, RF power, radar, computers, and specialized applications. The vast majority of these tubes have been replaced by semiconductors, leaving only a few types in regular manufacture and use.

Before we discuss these remaining applications, let's talk about the structure of modern tubes. All modern vacuum tubes are based on the concept of the Audion--a heated "cathode" boils off electrons into a vacuum; they pass through a grid or many grids , which control the electron current; the electrons then strike the anode plate and are absorbed. By designing the cathode, grid s and plate properly, the tube will make a small AC signal voltage into a larger AC voltage, thus amplifying it.

By comparison, today's transistor makes use of electric fields in a crystal which has been specially processed--a much less obvious kind of amplifier, though much more important in today's world.

Figure 3 Inside a miniature tube shows a typical modern vacuum tube. It is a glass bulb with wires passing through its bottom, and connecting to the various electrodes inside. Before the bulb is sealed, a powerful vacuum pump sucks all the air and gases out. This requires special pumps which can make very "hard" vacuums. To make a good tube, the pump must make a vacuum with no more than a millionth of the air pressure at sea level one microTorr, in official technical jargon.

The "harder" the vacuum, the better the tube will work and the longer it will last. Making an extremely hard vacuum in a tube is a lengthy process, so most modern tubes compromise at a level of vacuum that is adequate for the tube's application.

When the filament is heated white-hot about degrees Celsius , the thorium moves to the outer surface of it and emits electrons.

The filament with thorium is a much better maker of electrons than the plain tungsten filament by itself. Nearly all big power tubes used in radio transmitters use thoriated filaments, as do some glass tubes used in hi-fi amps.

The thoriated filament can last a VERY long time, and is very resistant to high voltages. This can be either just a filament coated with a mixture of barium and strontium oxides and other substances, or it can be an "indirectly heated" cathode, which is just a nickel tube with a coating of these same oxides on its outer surface and a heating filament inside.

The cathode and oxide coating is heated orange-hot, not as hot as the thoriated filament--about degrees Celsius. These oxides are even better at making electrons than the thoriated filament. Because the oxide cathode is so efficient, it is used in nearly all smaller glass tubes. It can be damaged by very high voltages and bombardment by stray oxygen ions in the tube, however, so it is rarely used in really big power tubes.

And the life of the of a cathode is dependent on the cathode temperature, the degree of vacuum in the tube, and purity of the materials in the cathode. The plate, or anode, is the electrode that the output signal appears on. Because the plate has to accept the electron flow, it can get hot. Especially in power tubes. So it is specially designed to cool itself off, either by radiating heat through the glass envelope if it's a glass tube , or by forced-air or liquid cooling in bigger metal-ceramic tubes.

Some tubes use a plate made of graphite, because it tolerates high temperatures and because it emits very few secondary electrons, which can overheat the tube's grid and cause failure. See "H--the getter" below for more about the graphite plate.

In nearly all glass audio tubes, the control grid is a piece of plated wire, wound around two soft-metal posts. In small tubes the plating is usually gold, and there are two posts made of soft copper. Grids in big power tubes have to tolerate a lot of heat, so they are often made of tungsten or molybdenum wire welded into a basket form.

Some large power tubes use basket-shaped grids made of graphite see D below. Inside any modern amplifying tube, one of the things to avoid is called secondary emission.

This is caused by electrons striking a smooth metal surface. If many secondary electrons come out of the grid, it will lose control of the electron stream, so that the current "runs away", and the tube destroys itself. So, the grid is often plated with a metal that is less prone to secondary emission, such as gold. Special surface finishing is also used to help prevent secondary emission. The most widely used small triode, the 12AX7, is a dual triode which has become the standard small-signal amplifier in guitar amps.

Many glass power triodes are currently on the market, most of them aimed at amateur radio or high-end audio use. Power triodes come in "low-mu" low gain and "high-mu" high gain versions.

Low-mu triodes like the SVB have very low distortion and are used in high-end audio amplifiers, while high-mu triodes are used mostly in radio transmitters and big high-power audio amplifiers. Large ceramic-metal power triodes are often used in radio transmitters and to generate radio energy for industrial heating applications. Specialized triodes of many kinds are made for exotic applications, such as pulsed radars and high-energy physics work. This "screen" grid helps screen, or isolate, the control grid from the plate.

This is important is reducing the so-called Miller effect, which makes the capacitance between the grid and plate look much bigger than it really is. The screen also causes an electron-accelerating effect, increasing the tube's gain dramatically. The screen grid in a power tube carries some current, which causes it to heat up. For this reason, screen grids are usually coated with graphite, to reduce secondary emission and help keep the control grid cool. Many large radio and TV stations use giant metal-ceramic power tetrodes, which are capable of high efficiency when used as RF power amplifiers.

Power tetrodes are also sometimes used in amateur radio and industrial applications. Regular tetrodes are rarely used for audio applications because of an effect called "tetrode kink", caused by that secondary emission. Most of it is due to electrons bouncing off the plate, some from the screen.

This greatly increases distortion and can cause instability if not carefully dealt with in the design. See section F, "audio beam tetrodes", below. Large ceramic tetrodes are often called "radial beam tetrodes" or simply "beam tetrodes", because their electron emission forms a disc-shaped beam. The wires on their control and screen grids are aligned, a special trick which improves efficiency. The third grid is called a suppressor grid and is inserted between the plate and the screen grid.

It has very few wire turns, since its only job is to collect the stray secondary-emission electrons that bounce off the plate, and thereby eliminate the "tetrode kink". It is usually operated at the same voltage as the cathode. The EL34 is widely used in guitar and high-end amplifiers as the power output tube. The smaller EL84 is seen in lower-cost guitar amps. The SV83 is used in a few high-end and guitar amps, while the EF86 is used as a low-noise preamp in guitar amps and professional audio equipment.

One of the few large high-power pentodes is the 5CXB, often seen in radio transmitters. There were tubes with more than three grids. The pentagrid converter tube, which had five grids, was widely used as the front-end frequency converter in radio receivers.

Such tubes are no longer in production, having been fully replaced by semiconductors. This is a special kind of beam tetrode, with a pair of "beam plates" to constrain the electron beam to a narrow ribbon on either side of the cathode. Also, the control and screen grids have their wire turns aligned, much like the large ceramic tetrodes above.

Unlike the ceramic tetrodes, the grids are at a critical distance from the cathode, producing a "virtual cathode" effect. All this adds up to greater efficiency and lower distortion than a regular tetrode or pentode. The first popular beam tetrode was the RCA 6L6, introduced in Beam tetrodes still made today include the SV6L6GC and SVC; the former is most popular in guitar amplifiers, while the latter is the most common power tube in modern high-end audio amplifiers for the home.

Today this design is seen only in glass tubes used in audio amplifiers, not in ceramic power tubes. An oxide-coated cathode can't heat itself, and it has to be hot to emit electrons. So, a wire filament heater is inserted within the cathode. This heater has to be coated with an electrical insulation that won't burn up at the high temperatures, so it is coated with powdered aluminum oxide.

This is an occasional cause of failure in such tubes; the coating rubs off or cracks, so the heater can touch the cathode.

transistor frequency converter

Skip to main content. Showing: 12 24 36 48 Search this category:. Filament type triode power amplifier designed for service in the output stage of audio amplifiers where high output and low harmonic distortion are desired. Its ratings and characteristics are similar to those of the 2A3 and 6B4G.

An Elementary Superregenerative Circuit

An amplifier , electronic amplifier or informally amp is an electronic device that can increase the power of a signal a time-varying voltage or current. 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 proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain : the ratio of output voltage, current, or power to input. An amplifier is a circuit that has a power gain greater than one. 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 categorized in different ways. One is by the frequency of the electronic signal being amplified. For example, audio amplifiers amplify signals in the audio sound range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and GHz, and servo amplifiers and instrumentation amplifiers may work with very low frequencies down to direct current. Amplifiers can also be categorized by their physical placement in the signal chain ; a preamplifier may precede other signal processing stages, for example.

List of vacuum tubes

Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. On the Theory of Tubes with Two Control Grids Abstract: The plate current at constant screen and plate voltages in a tube having two well-shielded control grids acting in tandem on the same electron stream is shown to be equal to the product of two functions, each a function of the potential on one grid only. For the pentagrid mixer hexode as modulator and heterodyne detector, simplified equivalent circuits are shown to hold, whereby the desired-frequency output currents and voltages may be obtained by calculations similar to those for class A amplifiers.

Vacuum Tubes

In bygone days, before all of the computerized wonders of modern technology, one of the favorite gifts that one could receive during the holiday season was a shiny new radio. The recipient's age was of no matter, it could be a bright red Catalin table radio for grandma, a Snow White radio for little Susie, or a Lone Ranger set for little Johnny. By the late s, radios had become relatively small, lightweight and reliable. Although the grand console floor model, with its magnificent sound and often the ability to receive international shortwave broadcasts would remain popular until World War II, the little table sets were rapidly gaining popularity. They were often purchased as second sets, for the convenience of having a radio on the breakfast table, while the big console remained in the living room. Battery portables had their own following with those who wanted to remain in the know while on the go.

Roy J. Tellason's Web Pages

Australasian Radio Relay League. The wireless weekly : the hundred per cent Australian radio journal, Sydney: Wireless Press,. Citations are automatically generated and may require some modification to conform to exact standards. Copies Direct supplies reproductions of collection material for a fee. This service is offered by the National Library of Australia. This application requires JavaScript to be enabled. Please open your browser preferences and enable JavaScript, or use a browser with JavaScript capabilities. Skip to content Skip to search.

ゆうパケットまたは普通郵便 【購入金額15000円以上は宅配便】 BREED ブリード BULL TERRIER（ブルテリア）80gピンク金

Click here to order virtually any vacuum tube you might need. Back in , British scientist John Ambrose Fleming first showed his device to convert an alternating current signal into direct current. The "Fleming diode" was based on an effect that Thomas Edison had first discovered in , and had not put to useful work at the time.

6CS6 Pentagrid Class A Amplifier Miniature RCA Radiotron Electron Vacuum Tube

This is a list of vacuum tubes or thermionic valves. Before the advent of semiconductor devices, hundreds of tube types were used in consumer and industrial electronics; today only a few types are still used in specialized applications. The first character group is always a number, consisting of one to three numerals, and almost always represents the heater voltage to the nearest whole number. These numerals are followed by one or two letters assigned to the devices in some sort of semi-chronological order of development and introduction to the marketplace, and then another single numeral which represents the number of active elements in the tube including any internal screen plus the heater in indirectly heated tubes - electrodes connected together internally count as one. Sometimes a string of up to three Roman letters can be suffixed to the overall number; these generally delineate various revisions and improvements to the original model or different bulb shapes. For a detailed description of the RMA numbering system used for transmitting and special-purpose tubes, see RMA tube designation.

In electronics , a vacuum tube , electron tube in North America , thermionic valve , tube , or valve is a device controlling electric current through a vacuum in a sealed container. The container is often thin transparent glass in a roughly cylindrical shape. The simplest vacuum tube, the diode, is essentially an incandescent light bulb with an extra electrode inside. When the bulb's filament is heated white-hot, electrons are boiled off its surface and into the vacuum inside the bulb. If the extra electrode also called a "plate" or "anode" is made more positive than the hot filament, a direct current flows through the vacuum to the anode a demonstration of the Edison effect.

With grid rectification as shown, the increase in grid current when a carrier signal is applied causes an increase in grid voltage in the negative direction, consequently the average plate current of the grid detector decreases when a signal is applied. Grid detection is generally used in amateur receivers of limited r. Plate detection is more commonly used where detector sensitivity is of minor importance, since a larger signal can be handled with less distortion than with grid detection. This radio-frequency can be fed back into the grid circuit, as shown in C of Fig.