Pentodes Connected As Triodes
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El156 Audio Power
EL156 AUDIO POWER Gerhard Haas Thanks to its robustness, the legendary EL156 audio power pentode has found its way into many professional amplifier units. Its attraction derives not just from its appealing shape, but also from its impressive audio characteristics. We therefore bring you this classical circuit, updated using high- quality modern components. 28 elektor electronics - 3/2005 AMPLIFIER Return of a legend The EL156 was manufactured in the enough to give adequate sensitivity, electrolytic capacitor: this voltage is legendary Telefunken valve factory in even before allowing any margin for further filtered on the amplifier board. Ulm, near the river Danube in Ger- negative feedback. The ECC81 many. The EL156 made amplifiers with (12AT7), however, which has an open- It is not possible to build an ultra-lin- an output power of up to 130 W possi- loop gain of 60 and which can be oper- ear amplifier using the EL156 with a ble, using just two valves in the output ated with anode currents of up to high anode voltage. The same goes for stage and one driver valve. Genuine 10 mA, can be used to build a suitably the EL34. The output transformer is EL156s are no longer available new at low-impedance circuit. therefore connected in such a way that realistic prices, and hardly any are Two EL156s can be used to produce an the impedance of the grid connection available second-hand. The original output power of 130 W with only 6 % to the output valve is much lower than devices used a metal valve base which distortion. -
Valve Biasing
VALVE AMP BIASING Biased information How have valve amps survived over 30 years of change? Derek Rocco explains why they are still a vital ingredient in music making, and talks you through the mysteries of biasing N THE LAST DECADE WE HAVE a signal to the grid it causes a water as an electrical current, you alter the negative grid voltage by seen huge advances in current to flow from the cathode to will never be confused again. When replacing the resistor I technology which have the plate. The grid is also known as your tap is turned off you get no to gain the current draw required. profoundly changed the way we the control grid, as by varying the water flowing through. With your Cathode bias amplifiers have work. Despite the rise in voltage on the grid you can control amp if you have too much negative become very sought after. They solid-state and digital modelling how much current is passed from voltage on the grid you will stop have a sweet organic sound that technology, virtually every high- the cathode to the plate. This is the electrical current from flowing. has a rich harmonic sustain and profile guitarist and even recording known as the grid bias of your amp This is known as they produce a powerful studios still rely on good ol’ – the correct bias level is vital to the ’over-biased’ soundstage. Examples of these fashioned valves. operation and tone of the amplifier. and the amp are most of the original 1950’s By varying the negative grid will produce Fender tweed amps such as the What is a valve? bias the technician can correctly an unbearable Deluxe and, of course, the Hopefully, a brief explanation will set up your amp for maximum distortion at all legendary Vox AC30. -
The Development of the Vacuum Tube Creators
The Knowledge Bank at The Ohio State University Ohio State Engineer Title: The Development of the Vacuum Tube Creators: Jeffrey, Richard B. Issue Date: May-1928 Publisher: Ohio State University, College of Engineering Citation: Ohio State Engineer, vol. 11, no. 7 (May, 1928), 9-10. URI: http://hdl.handle.net/1811/34260 Appears in Collections: Ohio State Engineer: Volume 11, no. 7 (May, 1928) THE OHIO STATE ENGINEER The Development of the Vacuum Tube By RICHARD B. JEFFREY, '31 The history of the vacuum tube began with the discovery of the Edison Effect. This, like a great many other important discoveries, was an acci- dent. Edison, while experimenting with his in- candescent lamps, had placed more than one fila- output ment in the same bulb, and he noticed that if one of the filaments was held positive with respect to the other a current would flow through the bulb. He also found that this positive element, or, as it is now called, plate, did not have to be hot to sustain this current flow. This phenomenon li—- H was known for some time as a curiosity, but noth- 1 +90 to \35 ing more. Then Fleming, an English experiment- +4-5 er, noticed that if an alternating current were The screen-qrid tube (tetrode). applied to this plate the current would flow only plicated system by making use of the rectifying when the plate was positive. In other words, the properties of a crystal, notably galena. When tube acted as a rectifier, allowing the current to signals were received in this way it was the signal flow in only one direction. -
Operation, Tetrode, Pentode in the Single-Ended, Class-A
10-76 10. Guitar Amplifiers 10.5.1 Single-ended (class A)-operation, tetrode, pentode In the single-ended, class-A power-stage, one (single) power-tube operates in common- cathode configuration with the output transformer being part of the plate circuit (transformer- coupling). Without AC-drive (“quiescent state”), a stable balance appears – it is called the operating point (OPP). The characteristics shown in Fig. 10.5.2 yield an OPP at 250 V and 48 mA, if a voltage of -7.5 V between (control) grid (g1) and cathode is chosen. This can be done e.g. by using a cathode-resistor of 142 Ω. The cathode-current (the sum of the 48-mA- plate-current and the 5-mA-screen-grid-current) will then generate a positive cathode-voltage of + 7.5 V (relative to ground). With the control-grid at ground-potential (Ug1 = 0) a control- grid-to-cathode-voltage of -7.5 V results (i.e. the control grid is negative vs. the cathode). Fig. 10.5.2: Output characteristics of the EL84, power-stage circuit (single-ended class-A operation). AP = OPP As a drive signal appears (Ug1 ≠ 0), plate-voltage and –current change. As a first approach, it will be sufficient to consider the transformer in the plate-circuit as a large inductance connected in parallel with an ohmic resistor (Chapter 10.6). In this model we have only pure DC flowing through the inductance, and only pure AC flowing through the resistor. With a drive-signal present, the Ua/Ia-point will move along the load-line given in Fig. -
Philips DEALING with TECHNICAL PROBLEMS
VOL. 5 N~. 3 . Philips DEALING WITH TECHNICAL PROBLEMS. RELATING TO THE PRODUCTS, PROCESSES AND. INVESTIGATIONS OF N.V. PHILIPS' GLOEILAMPENFABRIEKEN EDITED BY THE RESEARCH LABORATORY OF N.V. PHILIPS' GLOEILAMPENFABRIEKEN, EINDHOVEN, HOLLAND TESTING A~PLIFIER OUTPUT VALVES BY MEANS OF THE 'CAT~ODE RAY TUBE hy A. J. HEINS van der VEN. 621.317.755: 621.396.645 I n testing amplifier output valves, the most important data are contained in the In' v.. diagram if one knows over which part of the diagram the values of voltage and current prevailing during operatien range, i;e. if the position of the load line is known. The la- Vn 'diagrams as well as the load lines can very easily b~ obtained with the help of a 'cathode ray tube. The necessary apparatus is described in this article. A number of auxiliary ar- rangernents are also studied, by which the axes and the necessary calibration lines in the diagram can be traced on the fluorescent screen, and which make it possible to. cause the diagrams of two .output valves which are to be compared to appear simultancously on the screen. In order to obtain the load line in the correct place in the diagram, use must he made of dir'ect current push-pull amplifiers for the deflection voltages of the cathode ray tube. The position of the load line upon inductive loading is discussed and explained by a number of examples. In conclusion one,npplication of the instaflation in the develop- ment of output pentodes is dealt with. If one wishes to characterize briefly the perfor- quantrties are to some degree dependent _on the mance of an output valve of !tn amplifier or radio loading impedance which is included in the anode set, it is enough to give the sensitivity, the distor- circuit, it is first necessary to find out how the loa'd- tion as a function of the power output, and in some ing of the ~alve is e~pl'esse~ in the Ia- V~ curve.' , cases the maximum power which can he delivered mA without grid current flowing. -
Tutorial: Adding a Control Grid to a High-Current Electron Gun
Tutorial: adding a control grid to a high-current electron gun Stanley Humphries, Copyright 2012 Field Precision PO Box 13595, Albuquerque, NM 87192 U.S.A. Telephone: +1-505-220-3975 Fax: +1-617-752-9077 E mail: techinfo@fieldp.com Internet: http://www.fieldp.com 1 Recently, I was asked to consider whether a control grid consisting of parallel or crossed wires could be added to an existing space-charge-limited electron gun for beam modulation. I identified two main questions: • Because considerable effort had been invested in the gun design, would it possible to add the grid without significantly changing the macro- scopic beam optics? • What was the contribution to the angular divergence of the beam rel- ative to the focal requirements? With regard to first question, the best approach would be to locate the wire grid at the former position of the cathode surface and to move the cathode a short distance upstream. The grid would be attached to the focus electrode bounding the former cathode surface. Figure 1 is a schematic view of the cathode-grid region. The values of D and Vc should be chosen to generate an electron current density je equal to the space-charge limited design value in the main acceleration gap. In this way, the grid surface would act almost like the original cathode, preserving the gun optics. There are two options to fabricate a grid: 1) parallel wires with spacing W or 2) a crossed grid with square openings with side length W . For a rough estimate, I did not consider the effect of the wire width. -
Eimac Care and Feeding of Tubes Part 3
SECTION 3 ELECTRICAL DESIGN CONSIDERATIONS 3.1 CLASS OF OPERATION Most power grid tubes used in AF or RF amplifiers can be operated over a wide range of grid bias voltage (or in the case of grounded grid configuration, cathode bias voltage) as determined by specific performance requirements such as gain, linearity and efficiency. Changes in the bias voltage will vary the conduction angle (that being the portion of the 360° cycle of varying anode voltage during which anode current flows.) A useful system has been developed that identifies several common conditions of bias voltage (and resulting anode current conduction angle). The classifications thus assigned allow one to easily differentiate between the various operating conditions. Class A is generally considered to define a conduction angle of 360°, class B is a conduction angle of 180°, with class C less than 180° conduction angle. Class AB defines operation in the range between 180° and 360° of conduction. This class is further defined by using subscripts 1 and 2. Class AB1 has no grid current flow and class AB2 has some grid current flow during the anode conduction angle. Example Class AB2 operation - denotes an anode current conduction angle of 180° to 360° degrees and that grid current is flowing. The class of operation has nothing to do with whether a tube is grid- driven or cathode-driven. The magnitude of the grid bias voltage establishes the class of operation; the amount of drive voltage applied to the tube determines the actual conduction angle. The anode current conduction angle will determine to a great extent the overall anode efficiency. -
History of Thethermionic Tube / Valve / Vacuum
History of theThermionic Tube / Valve / Vacuum Tube – Page 1 The following notes have been assembled by Phil (VK5SRP) from original material and material from several web sites, including Wikipedia for a class run at the North East Radio Club, South Australia January 2016. 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/heater. This type is called a thermionic tube or thermionic valve. A Photo-tube, 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. Although thermionic emission was originally reported in 1873 by Frederick Guthrie, it was Thomas Edison's 1883 investigation that spurred future research, the phenomenon thus becoming known as the "Edison effect". Edison patented what he found, but he did not understand the underlying physics, nor did he have an inkling of the potential value of the discovery. It wasn't until the early 20th century that the rectifying property of such a device was utilised, most notably by John Ambrose Fleming, who used the Diode tube to detect (demodulate) radio signals. Lee De Forest's 1906 "Audion" was also developed as a radio detector, and soon led to the development of the Triode tube. -
The Venerable Triode
The Venerable Triode The very first gain device, the vacuum tube Triode, is still made after more than a hundred years, and while it has been largely replaced by other tubes and the many transistor types, it still remains popular in special industry and audio applications. I have some thoughts on why the Triode remains special for audio amplifiers (apart from sentimental value) that I would like to share. But first, a quick tutorial about Triodes: The earliest Triode was Lee De Forest's 1906 “Audion”. Over a hundred years development has resulted in many Triodes, large and small. The basic design has remained much the same. An evacuated container, usually glass, holds three signal connections, seen in the drawing as the Cathode, Grid and Plate (the Plate is also referred to as the Anode). In addition you see an internal heater, similar to a light bulb filament, which is used to heat the Cathode. Triode operation is simple. Electrons have what's known as “negative electrostatic charge”, and it is understood that “like” charges physically repel each other while opposite charges attract. The Plate is positively charged relative to the Cathode by a battery or other voltage source, and the electrons in the Cathode are attracted to the Plate, but are prevented by a natural tendency to hang out inside the Cathode and avoid the vacuum. This is where the heater comes in. When you make the Cathode very hot, these electrons start jumping around, and many of them have enough energy to leave the surface of the Cathode. -
A Relatively Simple Device for Recording Radiation Intensities in The
A RELATIVELY SIMPLE DEVICE FOR RECORDING RADIATION INTENSITIES IN HE ULTRAVIOLET PORTION OF THE SPECTRUM by HENRY WALLACE HENDRICKS A THESIS submitted to OREGON STATE COLLEGE in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE June 19S0 APPROVED: Professor of Physics In Charge of Major Chairman of School Graduate Committee Dean of Graduate School ACKN OWLEDGMENT Sincere appreciation and thanks are expressed to Dr. Weniger for his interest and assistance in the preparation of this thesis. TABLE OF CONThNTS a ge I NTROD[JCTION . ..... , . i Statement of . Problem . i Some Basic Information about Ultraviolet, Sun and Sky Radiation, Its Biological Etc. Effectiveness, . 1 INSTRUMLNTS FOR RECORDING ULTRAVIOLET INTENSITIES . 3 DESIGNOONSIDERATIONS. ... .. .. The R e e e i y e . r ....... The . Receiving Circuit . 9 The R e c o e . rd r . 9 . ThePowerSupply . .10 EX>ERIMENTAL . 1)EVELOPMENT . 11 THE FINAL CIRCUIT AND . 7OER SUPPLY . 16 PREPARATION AND SILVERING OF THE QUARTZ PLATES . 20 THERECEIVERUNIT..................23 TESTOFAPPARATtJS . .26 Adjustment8 . 26 Results and Conclusions . 27 . Data . 3]. BILIOGRAPHY . 37 LIST OF ILLUBTRATIONS Figure Page J. Spectral Sensitivfty of the S Photocathode 6 2 OriginalCircuit . 12 3 First Vacuum Tube Circuit . 12 Lj. Variation of the Counts per Minute with Filament Voltage . 11i The Final Circuit . ........ 17 6 The Power Suoply, Counter and Receiver . 22 The 7 Receiver ............... 2)4. 8 Step-diagram from Data ObtaIned on MaylO,l9O ............. 28 9 Step-diagram from Data Obtained on Mayll,l9O ............. 29 10 Step-diagram from Data Obtained on Mayl2,l95O ......... .. 30 A RELATIVELY SIMPLE DEVICE FOR RECORDING RADIATION .LNTENSITIES IN T}IE ULTRAVIOLET PORTION OF THE SPECTRUM INTRODUCTION Statement of Problem The purpose of this thesis is to develop a more or less portable aiaratua that will measure ultraviolet energy in or near the erythemal region. -
Sept. 27, 1938. H. J. Mcarthy 2,131,538 INVENTOR
Sept. 27, 1938. H. J. McArthy 2,131,538 WAWE SIGNALING SYSTEM Filed Dec. 31, 1936 INVENTOR CAPACITY OF CONDENSER 8 N m fid. AORNEY Patented Sept. 27, 1938 2,131,538 UNITED STATES PATENT OFFICE. 2,131,538 WAVE SIGNALENG SYSTEM Henry J. McCarthy, Danvers, Mass., assignor to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Application December 31, 1936, Seria No. 8,532 4 Claims. (C. 179-11) : . This invention relates to Wave. Signaling Sys velope either of the metal or glass type. Suitably tems and more especially to such systems as supported within the envelope is a pentode employ electron discharge tubes of the suppreSSor mount comprising an electron emitting cathode grid type. 2. With its insulated heater filament 3; a control 5 The invention is in the nature of an improve grid 4; a shield grid 5; a suppressor grid 6; and ment. On the type of System disclosed in appli an anode or plate. It will be understood that cation Serial No. 13,047, filed March 26th, 1935. any Well-known structure and arrangement of There is disclosed in said application a System the electrodes may be employed, for example the employing a pentode tube of the Suppressor grid mount may be similar to that embodied in the O type Wherein the suppressing action is achieved tubes designated commercially by the type num 10: Without employing a conductive or metallic con bers 39/44, 41, 57, 78 and the like and while the nection between the Suppressor grid and the invention is primarily applicable to radio fre cathode. -
Precise Db Monitoring with Eye Tubes This Circuit for Use with Eye Tubes Eliminates Variations for Precise and Accurate Signal Measurements
tubes Precise dB Monitoring with Eye Tubes This circuit for use with eye tubes eliminates variations for precise and accurate signal measurements. By Joe Sousa uning eye, or indicator, tubes came into use before World War II to help tune radio re- ceivers by indicating signal strength. This was helpful to reduce Tdistortion and adjacent channel inter- ference that would result if the radio were tuned too far from the center of the channel. The eye tubes were de- veloped as a cheaper alternative to the needle movement meters. It was not until the 1960s that needle meters were made economically enough in Japan to displace indicator tubes. During the decades from the 1930s to PHOTO 1: EM84/6FG6 with triode grid input at 0V, –3V, and –23V. the 1960s, when tuning indicator tubes were in production, they found wide use of the tube. The green rectangles grow to deflect the output beam on the fluo- in instrumentation as a low-cost alterna- longitudinally, as the input signal grows rescent target painted on the side of the tive to the needle meter. Capacitor mea- more negative (Photo 1). At full signal glass envelope. The 470k plate resistor surement bridges and tube testers were strength, the two among the more common instruments rectangles meet in making use of these inexpensive indica- the center, form- tor tubes. ing a solid rect- By the 1950s, indicator tube design angle 1.5˝ long. had matured enough that good preci- Figure 1 shows sion could be obtained for use as re- the internal ar- cording level meters in open-reel tape rangement of the recorders.