Jones Valve Amplifiers

4. Auflage 2011
ISBN: 978-0-08-096641-0
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 700 Seiten

Valve Amplifiers has been recognized as the most comprehensive guide to valve amplifier design, analysis, modification and maintenance. It provides a detailed presentation of the rudiments of electronics and valve design for engineers and non-experts. The source also covers design principles and construction techniques to help end users build their own tool from scratch designs that work. The author's approach walks the reader through each step of designing and constructing, starting with an overview of the essential working principles of valve amplifiers, the simple and complex stages, the process of linking the stages, and completing the design. The book is comprised of seven chapters all of which include a DIY guide discussion of practical aspects. The text starts with familiarization of the fundamentals of electronics, which are essential for designing and building valve amplifiers. Particular attention has been paid to providing solutions for questions that are commonly asked and faced by beginners in valve designing and construction. Valve Amplifiers is a masterful hands-on guide for both experts and novices who work with tube audio equipment, and for electronic hobbyists, audio engineers, and audiophiles. - The practical guide to analysis, modification, design, construction and maintenance of valve amplifiers - The fully up-to-date approach to valve electronics - Essential reading for audio designers and music and electronics enthusiasts alike

Autoren/Hrsg.

Jones, Morgan

Inhaltsverzeichnis

1;Front Cover;1
2;Valve Amplifiers;4
3;Copyright Page;5
4;Contents;6
5;Preface;10
6;Dedication;12
7;Acknowledgements;14
8;1. Circuit Analysis;16
8.1;Mathematical Symbols;16
8.2;Electrons and Definitions;17
8.2.1;Batteries and Lamps;19
8.2.2;Ohm’s Law;20
8.2.3;Power;21
8.2.4;Kirchhoff’s Laws;22
8.2.5;Resistors in Series and Parallel;24
8.3;Potential Dividers;29
8.3.1;Equivalent Circuits;29
8.3.2;The Thévenin Equivalent Circuit;30
8.3.3;The Norton Equivalent Circuit;33
8.3.4;Units and Multipliers;34
8.3.5;The Decibel;35
8.4;Alternating Current (AC);36
8.4.1;The Sine Wave;36
8.4.2;The Transformer;39
8.4.3;Capacitors, Inductors and Reactance;40
8.4.4;Filters;42
8.4.5;Time Constants;45
8.4.6;Resonance;46
8.4.7;RMS and Power;48
8.4.8;The Square Wave;49
8.4.9;Square Waves and Transients;50
8.4.10;Random Noise;55
8.5;Active Devices;56
8.5.1;Conventional Current Flow and Electron Flow;56
8.6;Silicon Diodes;57
8.6.1;Voltage References;58
8.7;Bipolar Junction Transistors (BJTs);60
8.7.1;The Common Emitter Amplifier;62
8.7.2;Considering DC Conditions;64
8.7.3;Input and Output Resistances;64
8.7.4;The Emitter Follower;66
8.7.5;The Darlington Pair;67
8.8;General Observations on BJTs;67
8.9;Feedback;68
8.9.1;The Feedback Equation;68
8.9.2;Practical Limitations of the Feedback Equation;69
8.9.3;Feedback Terminology and Input and Output Impedances;70
8.10;The Operational Amplifier;71
8.10.1;The Inverter and Virtual Earth Adder;72
8.10.2;The Non-Inverting Amplifier and Voltage Follower;73
8.10.3;The Integrator;75
8.10.4;The Charge Amplifier;75
8.10.5;DC Offsets;77
8.11;References;78
8.12;Recommended Further Reading;78
9;2. Basic Building Blocks;80
9.1;The Common Cathode Triode Amplifier;80
9.1.1;Limitations on Choice of the Operating Point;83
9.1.2;Conditions at the Operating Point;85
9.1.3;Dynamic, or AC, Parameters;88
9.1.4;Cathode Bias;91
9.1.5;The Effect on AC Conditions of an Unbypassed Cathode Bias Resistor;93
9.1.6;The Cathode Decoupling Capacitor;94
9.1.7;Choice of Value of Grid-Leak Resistor;96
9.1.8;Choice of Value of Output Coupling Capacitor;98
9.1.9;Miller Capacitance;98
9.1.10;Reducing Output Resistance of the Previous Stage;100
9.1.11;Guided-Grid, or Beam, Triodes;100
9.2;The Tetrode;101
9.3;The Beam Tetrode and the Pentode;102
9.3.1;The Significance of the Pentode Curves;104
9.3.2;Using the EF86 Small-Signal Pentode;106
9.4;The Cascode;109
9.5;The Charge Amplifier;117
9.6;The Cathode Follower;118
9.7;Sources and Sinks: Definitions;122
9.8;The Common Cathode Amplifier as a Constant Current Sink (CCS);124
9.8.1;Pentode Constant Current Sinks;126
9.9;The Cathode Follower with Active Load;128
9.10;The White Cathode Follower;129
9.10.1;Analysis of the Self-Contained White Cathode Follower;129
9.10.2;The White Cathode Follower as an Output Stage;132
9.11;The µ-Follower;133
9.11.1;The Importance of the AC Loadline;137
9.11.2;Upper Valve Choice in the µ-Follower;137
9.11.3;Limitations of the µ-Follower;138
9.12;The Shunt-Regulated Push–Pull Amplifier (SRPP);140
9.13;The ß-Follower;143
9.14;The Cathode-Coupled Amplifier;145
9.15;The Differential Pair;148
9.15.1;Gain of the Differential Pair;150
9.15.2;Output Resistance of the Differential Pair;150
9.15.3;AC Balance of the Differential Pair and Signal at the Cathode Junction;151
9.15.4;Common-Mode Rejection Ratio (CMRR);151
9.15.5;Power Supply Rejection Ratio (PSRR);153
9.16;Semiconductor Constant Current Sinks;154
9.16.1;Using Transistors as Active Loads for Valves;157
9.16.2;Optimising rout by Choice of Transistor Type;160
9.16.3;Field-Effect Transistors (FETs) as Constant Current Sinks;162
9.16.4;Designing Constant Current Sinks Using the DN2540N5;164
9.17;References;168
9.18;Recommended Further Reading;169
10;3. Dynamic Range: Distortion and Noise;170
10.1;Distortion;170
10.1.1;Defining Distortion;170
10.1.2;Measuring Non-Linear Distortion;171
10.1.3;Distortion Measurement and Interpretation;172
10.1.4;Choosing the Measurement;173
10.1.5;Refining Harmonic Distortion Measurement;174
10.1.6;Weighting of Harmonics;174
10.1.7;Summation and Rectifiers;175
10.1.8;Alternative Rectifiers;177
10.1.9;Noise and THD+N;177
10.1.10;Spectrum Analysers;178
10.2;Digital Concepts;178
10.2.1;Sampling;179
10.2.2;Scaling;179
10.2.3;Quantisation;180
10.2.4;Number Systems;180
10.2.5;Precision;180
10.3;The Fast Fourier Transform (FFT);181
10.3.1;The Periodicity Assumption;182
10.3.2;Windowing;182
10.3.3;How the Author’s Distortion Measurements Were Made;183
10.4;Designing for Low Distortion;184
10.5;Signal Amplitude;184
10.5.1;Cascodes and Distortion;187
10.6;Grid Current;188
10.6.1;Distortion due to Grid Current at Contact Potential;188
10.6.2;Distortion due to Grid Current and Volume Controls;189
10.6.3;Operating with Grid Current (Class A2);190
10.7;Distortion Reduction by Parameter Restriction;192
10.8;Distortion Reduction by Cancellation;195
10.8.1;Differential Pair Distortion Cancellation;197
10.8.2;Push–Pull Distortion Cancellation;199
10.8.3;The Western Electric Harmonic Equaliser;199
10.8.4;Side-Effects of the Harmonic Equaliser;201
10.9;DC Bias Problems;203
10.9.1;Cathode Resistor Bias;203
10.9.2;Grid Bias (Rk=0);205
10.9.3;Rechargeable Battery Cathode Bias (rk=0);206
10.9.4;Diode Cathode Bias (rk˜0);206
10.9.5;Constant Current Sink Bias;210
10.10;Individual Valve Choice;211
10.10.1;Which Valves Were Explicitly Designed to be Low Distortion?;211
10.10.2;Carbonising of Envelopes;213
10.10.3;Deflecting Electrons;213
10.10.4;Testing to Find Low-Distortion Valves;214
10.10.5;The Test Circuit;214
10.10.6;Audio Test Level and Frequency;215
10.10.7;Test Results;215
10.10.8;Interpretation;218
10.10.9;A Convention;220
10.10.10;Alternative Medium-µ Valves;220
10.10.11;Weighted-Distortion Results;221
10.10.12;Overall Conclusions;221
10.11;Coupling from One Stage to the Next;222
10.11.1;Blocking;223
10.11.2;Transformer Coupling;225
10.11.3;Low Frequency Step Networks;225
10.11.4;Level Shifting and DC Coupling;226
10.11.5;A DC Coupled Class A Electromagnetic Headphone Amplifier;228
10.11.6;Using a Norton Level Shifter;231
10.12;Distortion and Negative Feedback;234
10.13;Carbon Resistors and Distortion;237
10.14;Noise;237
10.15;Noise from Resistances;238
10.15.1;Noise from Resistive Volume Controls;238
10.16;Noise from Amplifying Devices;239
10.16.1;Grid Current Noise and the Poisson Distribution;241
10.16.2;Electrometers and Grid Current;241
10.17;Noise in DC References;245
10.17.1;How the Author’s DC Reference Noise Measurements Were Made;245
10.17.2;Gas Reference Noise Measurements;247
10.17.3;Variation of Gas Reference Noise with Operating Current;247
10.17.4;Semiconductor Reference Noise Measurements and Statistical Summation;247
10.17.5;Variation of Zener Reference Noise with Operating Current;249
10.17.6;Noise of the Composite Zener Compared to a 317;250
10.17.7;Red LED Noise;251
10.18;References;251
10.19;Recommended Further Reading;252
11;4. Component Technology;254
11.1;Resistors;254
11.1.1;Preferred Values;254
11.1.2;Heat;255
11.1.3;Metal Film Resistors;256
11.1.4;Power (Wirewound) Resistors;259
11.1.5;Ageing Wirewound Resistors;259
11.1.6;Noise and Inductance of Wirewound Resistors;260
11.1.7;Non-Inductive Thick Film Power Resistors;263
11.2;General Considerations on Choosing Resistors;263
11.2.1;Tolerance;263
11.2.2;Heat;263
11.2.3;Voltage Rating;264
11.2.4;Power Rating;264
11.3;Capacitors;264
11.3.1;The Parallel Plate Capacitor;264
11.3.2;Reducing the Gap Between the Plates and Adding Plates;265
11.3.3;The Dielectric;265
11.4;Different Types of Capacitors;266
11.4.1;Air Dielectric, Metal Plate (er˜1);268
11.4.2;Plastic Film, Foil Plate Capacitors (2

Leseproben

Chapter 1

Circuit Analysis

Publisher Summary

This chapter illustrates Circuit Analysis. Electrons are charged particles. Charged objects are attracted to other charged particles or objects. Charged objects come in two forms—negative and positive. Unlike charges attract, and like charges repel. Electrons are negative and positrons are positive, but while electrons are stable in the universe, positrons encounter an electron almost immediately after production, resulting in mutual annihilation and a pair of 511 keV gamma rays. An electron is very small, and does not have much of a charge, so one needs a more practical unit for defining charge. That practical unit is the coulomb (C). One could say that 1 C of charge had flowed between one point and another, which would be equivalent to saying that approximately 6,240,000,000,000,000,000 electrons had passed, but much handier. Simply being able to say that a large number of electrons had flowed past a given point is not in it very helpful. One might say that a billion cars have traveled down a particular section of motorway since it was built, but if he/she were planning a journey down that motorway, he or she would want to know the flow of cars per hour through that section.

In order to look at the interesting business of designing and building valve amplifiers, we need some knowledge of electronics funmentals. Unfortunately, fundamentals are not terribly interesting, and to cover them fully would consume the entire book. Ruthless pruning is, therefore, necessary to condense what is needed in one chapter.

It is thus with deep sorrow that the author has had to forsaken complex numbers and vectors, whilst the omission of differential calculus is a particularly poignant loss. All that is left is ordinary algebra, and although there are of equations, they are timid, miserable creatures and quite defenceless.

If you are comfortable with basic electronic terms and techniques, then please feel free to go directly to Chapter 2, where valves appear.

Mathematical Symbols

Unavoidably, a number of mathematical symbols are used, some of which you may have forgotten, or perhaps not previously met:

= is totally equivalent to

= equals

˜ is approximately equal to

? is proportional to

? is not equal to

> is greater than

< is less than

= is greater than, or equal to,

= is less than, or equal to,

As with the = and ? symbols, the four preceding symbols can have a slash through them to negate their meaning ( ? , a is not less than ).

v the number which when multiplied by itself is equal to (square root)

multiplied by itself times. 4=××× ( to the power )

± plus or minus

8 infinity

° degree, either of temperature (°C), or of an angle (360° in a circle)

parallel, either parallel lines, or an electrical parallel connection

? a small change in the associated value, such as ?gk.

Electrons and Definitions

Electrons are particles. Charged objects are attracted to other charged particles or objects. A practical demonstration of this is to take a balloon, rub it briskly against a jumper and then place the rubbed face against a wall. Let it go. The balloon remains stuck to the wall. This is because we have charged the balloon, and so there is an attractive force between it and the wall. (Although the wall was initially uncharged, placing the balloon on the wall induced a charge.)

Charged objects come in two forms: negative and positive. Unlike charges attract, and like charges repel. Electrons are negative and positrons are positive, but whilst electrons are stable in our universe, positrons encounter an electron almost immediately after production, resulting in mutual annihilation and a pair of 511 keV gamma rays.

If we don’t have ready access to positrons, how can we have a positively charged object? Suppose we had an object that was negatively charged, because it had 2,000 electrons clustered on its surface. If we had another, similar, object that only had 1,000 electrons on its surface, then we would say that the first object was more negatively charged than the second, but as we can’t count how many electrons we have, we might just as easily have said that the second object was more positively charged than the first. It’s just a matter of which way you look at it.

To charge our balloon, we had to do some work and use energy. We had to overcome friction when rubbing the balloon against the woollen jumper. In the process, electrons were moved from one surface to the other. Therefore, one object (the balloon) has acquired an excess of electrons and is negatively charged, whilst the other object (woollen jumper) has lost the same number of electrons and is positively charged.

The balloon would, therefore, stick to the jumper. Or would it? Certainly it will be attracted to the jumper, but what happens when we place the two in contact? The balloon does not stick. This is because the fibres of the jumper were able to touch the whole of the charged area on the balloon, and the electrons were so attracted to the jumper that they moved back onto the jumper, thus neutralising the charge.

At this point, we can discard vague talk of balloons and jumpers because we have just observed electron flow.

An electron is very small, and doesn’t have much of a charge, so we need a more practical unit for defining charge. That practical unit is the (). We could now say that 1 C of charge had flowed between one point and another, which would be equivalent to saying that approximately 6,240,000,000,000,000,000 electrons had passed, but much handier.

Simply being able to say that a large number of electrons had flowed past a given point is not in itself very helpful. We might say that a billion cars have travelled down a particular section of motorway since it was built, but if you were planning a journey down that motorway, you would want to know the flow of cars through that section.

Similarly in electronics, we are not concerned with the total flow of electrons since the dawn of time, but we do want to know about electron flow at any given instant. Thus, we could define the flow as the number of coulombs of charge that flowed past a point in one second. This is still rather long-winded, and we will abbreviate yet further.

We will call the flow of electrons , and as the coulomb/second is unwieldy, it will be redefined as a new unit, the (). Because the ampere is such a useful unit, the definition linking current and charge is usually stated in the following form.

(coulombs)=current(amperes)×time(seconds)

This is still rather unwieldy, so symbols are assigned to the various units: charge has symbol , current and time .

=It

This is a very useful equation, and we will meet it again when we look at capacitors (which store charge).

Meanwhile, current has been flowing, but why did it flow? If we are going to move electrons from one place to another, we need a force to cause this movement. This force is known as the electro motive force (EMF). Current continues to flow whilst this force is applied, and it flows from a higher potential to a lower potential.

If two points are at the same potential, no current can flow between them. What is important is the ().

A potential difference causes a current to flow between two points. As this is a new property, we need a unit, a symbol and a definition to describe it. We mentioned work being done in charging the balloon, and in its very precise and physical sense, this is how we can define potential difference, but first, we must define .

This very physical interpretation of work can be understood easily once we realise that it means that one joule of work would be done by moving one kilogramme a distance of one metre in one second. Since charge is directly related to the mass of electrons moved, the physical definition of work can be modified to define the force that causes the movement of charge.

Unsurprisingly, because it causes...