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Physics of Hi-Fi: Analog to Digital (420 Technical Illustrations)
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Contents
1 Introduction to Hi-Fi 1
2 Waves 14
3 Decibels 63
4 Loudspeakers 67
5 Electricity 112
6 Ampli�ers 138
7 Electromagnetism 153
8 Electromagnetic Waves and Tuners 173
9 Analog Recording and Playback 202
10 Digital Optical Recording & Playback 226
11 Digital Magnetic Recording & Playback 247
12 Heat 260
13 Mechanics 273
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List of Figures
1.1 Stereo process in recording and playback. : : : : : : : : : : : 21.2 Surround sound reproduction of audio information. : : : : : : 31.3 Storage or transmission of sound in stereo. : : : : : : : : : : : 31.4 Playback process in stereo. : : : : : : : : : : : : : : : : : : : 41.5 Elements of a receiver. : : : : : : : : : : : : : : : : : : : : : : 41.6 Example of basic connections to a receiver. : : : : : : : : : : 51.7 Elements of an integrated ampli�er. : : : : : : : : : : : : : : 51.8 Connections to an integrated ampli�er. : : : : : : : : : : : : : 61.9 All separate approach. : : : : : : : : : : : : : : : : : : : : : : 61.10 Connections in all-separate approach. : : : : : : : : : : : : : 71.11 Basic A/V System. : : : : : : : : : : : : : : : : : : : : : : : : 81.12 A/V receiver driving a surround-sound system. : : : : : : : : 91.13 Details of the tape monitor switch when listening to a sound
source with available tape recording. : : : : : : : : : : : : : : 101.14 Listening to a tape; tape switch in. : : : : : : : : : : : : : : : 111.15 A/V receiver with Dolby Pro Logic processor. : : : : : : : : : 121.16 Various wave forms. : : : : : : : : : : : : : : : : : : : : : : : 13
2.1 Phono record and an enlarged groove showing engraved waverepresenting sound. : : : : : : : : : : : : : : : : : : : : : : : : 15
2.2 Simpli�ed picture of a water wave; displaced water as a func-tion of position. : : : : : : : : : : : : : : : : : : : : : : : : : : 15
2.3 Details of one wave as a function of position. : : : : : : : : : 162.4 Large and small amplitude waves. : : : : : : : : : : : : : : : : 162.5 Time dependence of displacement of a point on a water wave. 172.6 Displacement as a function of time; time required to complete
one wave. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 172.7 Transverse wave on a string. : : : : : : : : : : : : : : : : : : : 182.8 Longitudinal waves along a solid bar. : : : : : : : : : : : : : : 18
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2.9 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 182.10 Sound requires a medium in which to propagate; in a vacuum
there is no sound propagation. : : : : : : : : : : : : : : : : : 192.11 Direct radiator speaker can move air like a drumhead. : : : : 192.12 Generation of sound by loudspeaker. : : : : : : : : : : : : : : 202.13 Disturbances created by loudspeaker; pressure changes cause
sound. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 212.14 Representation of sound created by a loudspeaker. : : : : : : 212.15 Wave Y has 4 times the power of wave X, but their ampli-
tudes di�er only by a factor of 2. : : : : : : : : : : : : : : : : 222.16 Re ection of a wave by an obstacle or a di�erent medium. : : 222.17 Speaker producing a pulse of sound in a hall. : : : : : : : : : 232.18 Paths of direct and re ected sound in a hall. : : : : : : : : : : 242.19 Direct and reverberant sound in a hall. : : : : : : : : : : : : : 252.20 Direct and reverberant sound contributions to sound in a hall. 262.21 Sound radiated by a speaker; as one moves away the intensity
decreases. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 272.22 Sound intensity through surface 2 is di�erent from that of 1. : 282.23 Observer and source at rest and in relative motion. : : : : : : 292.24 Doppler E�ect produced by speaker producing simultane-
ously 100 Hz and 1,000 Hz sound waves. : : : : : : : : : : : : 302.25 Sound wave in cold air entering hot air. : : : : : : : : : : : : 312.26 Refraction of a sound wave. : : : : : : : : : : : : : : : : : : : 312.27 Above a critical angle of incidence there is only re ection. : : 322.28 Sound travels in a curved hollow plastic tube by multiple
re ections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 332.29 Sound wave produced by a musical group; a complex wave. : 342.30 Simple sine waveform. : : : : : : : : : : : : : : : : : : : : : : 342.31 Comparison between one full wave and one rotation of a circle. 352.32 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 352.33 Addition of two waves out of phase by 180 degrees. : : : : : : 352.34 Constructive interference. : : : : : : : : : : : : : : : : : : : : 362.35 Destructive interference. : : : : : : : : : : : : : : : : : : : : : 372.36 Obstacle with aperture receiving high frequency waves. : : : : 382.37 Low frequency behavior of obstacle and aperture. : : : : : : : 392.38 Comparison of di�raction behavior of a room with opening
and a loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : : 402.39 Dispersion characteristics of a speaker. : : : : : : : : : : : : : 412.40 Standing wave produced by incident and re ected waves. : : : 41
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2.41 Simplest possible standing wave on a string. : : : : : : : : : : 422.42 Simplest standing wave on a string during one cycle. : : : : : 432.43 Second harmonic on a string showing position of nodes and
antinodes. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 432.44 Third harmonic on a string clamped at both ends. : : : : : : 432.45 Setting up a standing wave in a tube. : : : : : : : : : : : : : 442.46 Simplest standing wave in a tube open at both ends. : : : : : 452.47 Second harmonic in tube open at both ends. : : : : : : : : : : 452.48 Fundamental in a tube. : : : : : : : : : : : : : : : : : : : : : 452.49 Tube open at one end excited by a tuning fork. : : : : : : : : 462.50 Fundamental in tube open at one end. : : : : : : : : : : : : : 462.51 Next more complicated standing wave; the third harmonic. : 472.52 Fifth harmonic. : : : : : : : : : : : : : : : : : : : : : : : : : : 472.53 Standing wave in a tube 1 meter long; fundamental. : : : : : 472.54 Tube closed at both ends. : : : : : : : : : : : : : : : : : : : : 482.55 Fundamental of a tube closed at both ends. : : : : : : : : : : 482.56 Room where independent standing waves can be set up in the
x, y, and z directions. : : : : : : : : : : : : : : : : : : : : : : 492.57 A drumhead �xed at its edges and its fundamental mode of
vibration. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 502.58 Overtone on a drumhead. : : : : : : : : : : : : : : : : : : : : 512.59 Standing wave pattern on a Chladni plate. : : : : : : : : : : : 512.60 Complex wave created by the superposition of a 100 Hz fun-
damental and its fourth harmonic. : : : : : : : : : : : : : : : 522.61 Violin string plucked by a �nger and producing all sorts of
harmonics. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 532.62 Complex wave generated by plucking string. : : : : : : : : : : 542.63 Square wave; it is made up of many harmonics. : : : : : : : : 552.64 Spectrum of a square wave. : : : : : : : : : : : : : : : : : : : 562.65 Sawtooth wave and its harmonic content. : : : : : : : : : : : 572.66 Spectrum of a sawtooth wave. : : : : : : : : : : : : : : : : : : 582.67 A string bowed at its middle and harmonics which are excited. 592.68 String on a piano struck by hammer at a distance 1/10 the
string length from one end. : : : : : : : : : : : : : : : : : : : 602.69 Vibrations of an object at di�erent excitation frequencies. : : 602.70 Oscillations of a mass on a spring, undamped and damped
when submersed in oil. : : : : : : : : : : : : : : : : : : : : : : 612.71 Resonance of wine glass excited by sound. : : : : : : : : : : : 61
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2.72 Beats caused by the combination of two waves with slightlydi�erent frequencies. : : : : : : : : : : : : : : : : : : : : : : : 62
3.1 Decibel meter. : : : : : : : : : : : : : : : : : : : : : : : : : : 643.2 Receiver with volume control marked in dB. : : : : : : : : : : 643.3 Response of human ears at the threshold of hearing. : : : : : 643.4 Response of human ears for various sound levels: Fletcher-
Munson curves. : : : : : : : : : : : : : : : : : : : : : : : : : : 653.5 Outer ear approximated by a tube closed at one end. : : : : : 653.6 Measuring the frequency response of a speaker. : : : : : : : : 663.7 Frequency response of a speaker. : : : : : : : : : : : : : : : : 66
4.1 Role of loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : 684.2 Distortion of spectrum of original waveform by non- at fre-
quency response of speaker. : : : : : : : : : : : : : : : : : : : 694.3 Dispersion properties of speakers. : : : : : : : : : : : : : : : : 704.4 Two low frequency waves from speaker arriving at O. : : : : : 714.5 Two high frequency waves from speaker arriving at O. : : : : 724.6 Details of waves 2 and 1 at high frequencies. : : : : : : : : : : 734.7 Sound dispersion of a driver as the frequency is increased. : : 744.8 Division of audio spectrum for a three-way loudspeaker. : : : 754.9 Net e�ect of subdividing the whole audio range into three
sections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 764.10 Subdivision of audio spectrum in a two-way system. : : : : : 764.11 Amount of sound produced depends on volume displacement.
A is louder than B. : : : : : : : : : : : : : : : : : : : : : : : : 774.12 To produce same amount of sound by both drivers at the
same frequency, the small one has to move through a largerdistance than the big one. : : : : : : : : : : : : : : : : : : : : 78
4.13 Volume of air moved by loudspeaker as a function of frequencyto produce same loudness of sound. : : : : : : : : : : : : : : : 79
4.14 Low frequency and high frequency simple pendulums doingdi�erent amounts of work per second for same amplitude ofdisplacement. : : : : : : : : : : : : : : : : : : : : : : : : : : : 80
4.15 Balance between electrical power going to driver and the pro-duction of sound power and heat dissipation by driver. : : : : 80
4.16 Example of a loudspeaker whose e�ciency is less than 100%. 814.17 Basic cone speaker. : : : : : : : : : : : : : : : : : : : : : : : : 82
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4.18 Comparison of cone-shape over at shape for mechanical strengthwhen thin material is used. : : : : : : : : : : : : : : : : : : : 83
4.19 Modeling of diaphragm action by mass-spring oscillating sys-tem. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 84
4.20 Standing wave on diaphragm of driver. : : : : : : : : : : : : : 854.21 Standing wave around rim of diaphragm. : : : : : : : : : : : 854.22 Typical frequency response of a cone speaker. : : : : : : : : : 864.23 Ba�e problem in cone driver. : : : : : : : : : : : : : : : : : : 864.24 Front and rear of cone speakers are 180� out of phase. : : : : 874.25 Ba�e action. : : : : : : : : : : : : : : : : : : : : : : : : : : : 884.26 Two possible approaches for trapping rear sound in a speaker
by means of an enclosure. : : : : : : : : : : : : : : : : : : : : 884.27 E�ect of enclosure on frequency response of speaker. : : : : : 894.28 Reducing standing waves inside speaker enclosure. : : : : : : 904.29 Basic bass-re ex enclosure. : : : : : : : : : : : : : : : : : : : 914.30 Oscillating components of bass-re ex speaker. : : : : : : : : : 924.31 Splitting of original resonance into two new resonances in
bass-re ex system. : : : : : : : : : : : : : : : : : : : : : : : : 934.32 Resonant behavior, in-phase and out-of-phase, motion of strongly
coupled components of bass-re ex system. : : : : : : : : : : : 944.33 Coupled components of a bass-re ex speaker. : : : : : : : : : 954.34 Bass-re ex speaker using a passive radiator over the port. : : 964.35 Helmholtz resonator behaves like mass-spring system. : : : : 974.36 Bass-re ex speaker using a port or a duct. : : : : : : : : : : : 984.37 Acoustic labyrinth enclosure. : : : : : : : : : : : : : : : : : : 994.38 Change of frequency response of speaker when a small enclo-
sure is used. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1004.39 E�ect of small enclosure on frequency response of driver. : : : 1014.40 Transfer of energy from a bob to one of equal mass, and to
one of di�erent mass. : : : : : : : : : : : : : : : : : : : : : : : 1024.41 A horn for matching vibrations of a light diaphragm to a large
volume of air. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1034.42 Low frequency response of a horn. : : : : : : : : : : : : : : : 1034.43 Some common horn shapes. : : : : : : : : : : : : : : : : : : : 1044.44 Folded horn. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1054.45 Two-way horn loudspeaker with bass-re ex enclosure. : : : : 1064.46 Standing wave set up in a room with maxima and minima in
sound pressure. : : : : : : : : : : : : : : : : : : : : : : : : : : 107
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4.47 Re ected waves by a wall appear to come from behind thewall since it acts like a mirror. : : : : : : : : : : : : : : : : : 107
4.48 Stereo coverage in a room. : : : : : : : : : : : : : : : : : : : : 1084.49 Speaker phasing: speakers are in phase. : : : : : : : : : : : : 1084.50 Speaker phasing: speakers are out of phase. : : : : : : : : : : 1094.51 Geometry of a Bose 901 speaker. : : : : : : : : : : : : : : : : 1094.52 E�ect of equalizer on frequency response of Bose speakers. : : 1104.53 Bass horn in Klipsch horn speaker. : : : : : : : : : : : : : : : 1114.54 Graphic equalizer. : : : : : : : : : : : : : : : : : : : : : : : : 111
5.1 Example of an atom: a Helium atom. : : : : : : : : : : : : : 1135.2 Forces between charged objects; like charges repel and unlike
charges attract. : : : : : : : : : : : : : : : : : : : : : : : : : : 1145.3 Charged ping-pong balls repelling each other. : : : : : : : : : 1155.4 Electric �eld produced by a charged object. : : : : : : : : : : 1155.5 Electric �eld between two charged plates. : : : : : : : : : : : 1165.6 Examples of voltage sources: a battery, the output of a receiver.1165.7 Electrostatic speaker: basic principle and actual speaker. : : : 1175.8 Simpli�ed version of an electrostatic speaker at equilibrium. : 1175.9 Push-pull action by two plates on charged sheet. : : : : : : : 1185.10 An electrostatic speaker. : : : : : : : : : : : : : : : : : : : : : 1185.11 Some crystals under pressure produce positive and negative
charges on surface. : : : : : : : : : : : : : : : : : : : : : : : : 1195.12 Dimensional changes of a piezoelectric ceramic when a voltage
is applied. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1195.13 Bending action of a double piezoelectric driver. : : : : : : : : 1205.14 Pumping action of cone caused by bending of bimorph. : : : 1205.15 Typical piezo horn. : : : : : : : : : : : : : : : : : : : : : : : : 1215.16 Wire connected between two charged objects allows charges
to be transferred. : : : : : : : : : : : : : : : : : : : : : : : : : 1215.17 Flow of electric current from ampli�er to speaker. : : : : : : : 1225.18 Solid with atoms where electrons are tightly bound and which
does not conduct electricity under normal circumstances. : : 1225.19 Motion of one electron in a conductor in the presence of an
electric �eld. Changes of direction are due to scattering. : : : 1235.20 Temperature dependence of the electrical resistance in a con-
ductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1245.21 Superconductivity at Tc below which the resistance is zero. : 124
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5.22 The resistance to current or to water ow increases as thelength of a conductor or pipe increases. Resistance of 2 isdouble that of 1. : : : : : : : : : : : : : : : : : : : : : : : : : 125
5.23 By increasing the cross-sectional area of a conductor, resis-tance to current or water ow decreases. : : : : : : : : : : : : 125
5.24 Resistor with colored bands to specify its resistance value. : : 1265.25 Pure silicon, silicon doped with arsenic, and silicon doped
with gallium. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1265.26 Example of simple circuit. : : : : : : : : : : : : : : : : : : : : 1265.27 Model using water for electric circuit. : : : : : : : : : : : : : 1275.28 Comparison between DC and AC current. : : : : : : : : : : : 1285.29 Representation of a sound wave by an AC electrical signal. : 1285.30 Variable resistance between X and Y. : : : : : : : : : : : : : 1295.31 Fuse to protect speaker. : : : : : : : : : : : : : : : : : : : : : 1295.32 Two speakers connected in series to one channel of ampli�er. 1295.33 Model of series circuit. : : : : : : : : : : : : : : : : : : : : : : 1305.34 Parallel connection of two speakers to an ampli�er. : : : : : : 1305.35 Model of parallel connections. : : : : : : : : : : : : : : : : : : 1315.36 Parallel connections of hi-� components to house electrical
outlet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1315.37 Response of cone speaker to a force. : : : : : : : : : : : : : : 1325.38 Coil used to produce a magnetic �eld when a current ows
through it. It has inductance. : : : : : : : : : : : : : : : : : : 1335.39 Frequency dependence of impedance associated with induc-
tance. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1345.40 Charging of a capacitor. : : : : : : : : : : : : : : : : : : : : : 1345.41 Charging of a capacitor when polarity of voltage source is
reversed. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1355.42 Frequency dependence of impedance due to capacitance. : : : 1355.43 Inductance in series with woofer prevents high frequencies
from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 1365.44 Capacitance in series with tweeter. It prevents low frequencies
from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 1365.45 Capacitance and inductance in series with mid-range speaker
to prevent the high and low frequencies from reaching it. : : : 1375.46 Impedance curve of driver. : : : : : : : : : : : : : : : : : : : : 137
6.1 Importance of ampli�er in hi-� system. : : : : : : : : : : : : : 1396.2 Basic ampli�er. : : : : : : : : : : : : : : : : : : : : : : : : : : 139
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6.3 Ampli�er command for more current. : : : : : : : : : : : : : 1406.4 Ampli�er command for less current. : : : : : : : : : : : : : : 1406.5 Semiconductor junction. : : : : : : : : : : : : : : : : : : : : : 1416.6 Reverse-biased semiconductor junction. : : : : : : : : : : : : 1416.7 Forward-biased semiconductor junction. : : : : : : : : : : : : 1426.8 Symbol for diodes and its characteristics. : : : : : : : : : : : 1426.9 Recti�er action of a diode when an AC voltage is applied. : : 1426.10 Diagram of transistor and its circuit symbol for two possibilities.1436.11 Ampli�er action of transistor in a circuit compared to control
of water ow. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1436.12 Function of an ampli�er. : : : : : : : : : : : : : : : : : : : : : 1446.13 Ampli�er integrated on a chip. : : : : : : : : : : : : : : : : : 1446.14 Operational ampli�er with negative feedback. : : : : : : : : : 1446.15 Negative feedback corrects uctuations in gain. : : : : : : : : 1456.16 Positive feedback in large hall with a mike and a loudspeaker
system driven by mike. : : : : : : : : : : : : : : : : : : : : : : 1456.17 Volume control. : : : : : : : : : : : : : : : : : : : : : : : : : : 1466.18 Comparison of potentiometer action with energy of a ball on
a ladder. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1466.19 Bass and Treble controls. : : : : : : : : : : : : : : : : : : : : 1476.20 E�ect on signal spectrum of Bass and Treble controls. : : : : 1486.21 Action of LOW and HIGH �lters with 6 dB/octave attenua-
tion, and also with 18 db/octave attenuation. : : : : : : : : : 1486.22 Harmonic distortion by ampli�er. : : : : : : : : : : : : : : : : 1496.23 Non-linear gain of ampli�er. : : : : : : : : : : : : : : : : : : : 1496.24 IM distortion in ampli�er. : : : : : : : : : : : : : : : : : : : : 1506.25 Distortion increases sharply about power rating of ampli�er. : 1506.26 Clipping of waveform by ampli�er at high output levels be-
yond the rated value. : : : : : : : : : : : : : : : : : : : : : : : 1516.27 E�ect of noise from ampli�er. : : : : : : : : : : : : : : : : : : 1516.28 Comparing 2 ampli�ers with the same specs. Even though
their specs are the same, the ampli�ers will sound di�erent. : 1526.29 A-weighted method of measuring noise. : : : : : : : : : : : : 152
7.1 E�ect of current in a wire on compasses around it. : : : : : : 1547.2 Bar magnet has a north pole and a south pole. : : : : : : : : 1547.3 Cutting a bar magnet produces shorter magnets each with its
own respective north and south poles. : : : : : : : : : : : : : 1547.4 Magnetic dipole is the basic unit of magnetism. : : : : : : : : 155
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7.5 Unmagnetized piece of iron. : : : : : : : : : : : : : : : : : : : 1557.6 Alignment of domains in a piece of iron by a bar magnet. Iron
becomes magnetized. : : : : : : : : : : : : : : : : : : : : : : : 1567.7 Magnetic �eld around a bar magnet and a wire carrying a
current. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1567.8 Increasing the magnetic �eld produced by a current in a wire:
by forming a loop, and by using many loops. : : : : : : : : : 1577.9 An electromagnet. : : : : : : : : : : : : : : : : : : : : : : : : 1577.10 Determination of direction of magnetic �eld using �rst left-
hand rule. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1587.11 Rule for determining direction of magnetic �eld in an electro-
magnet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1587.12 First left-hand rule and how a cone speaker works. : : : : : : 1597.13 Force on wire carrying a current in a magnetic �eld. : : : : : 1597.14 The second left-hand rule showing direction of force on wire
carrying a current in a magnetic �eld. : : : : : : : : : : : : : 1607.15 Direction of force depends on orientation of current with re-
spect to magnetic �eld. : : : : : : : : : : : : : : : : : : : : : 1617.16 A Heil Speaker. : : : : : : : : : : : : : : : : : : : : : : : : : : 1627.17 One set of folds in Heil speaker. : : : : : : : : : : : : : : : : : 1637.18 Magnetic Planar Speaker. : : : : : : : : : : : : : : : : : : : : 1647.19 Forces on diaphragm when current direction is as indicated. : 1657.20 A bar magnet moving into a coil induces an electric current
in that coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1657.21 Induced current in coil by moving magnet. : : : : : : : : : : : 1667.22 Signi�cance of relative motion between magnet and coil. : : : 1677.23 Direction of induced current (wrong). : : : : : : : : : : : : : 1677.24 Direction of induced current (correct). : : : : : : : : : : : : : 1687.25 Schematic of a transformer and its circuit symbol. : : : : : : 1697.26 Step-up transformer. : : : : : : : : : : : : : : : : : : : : : : : 1707.27 Step-down transformer. : : : : : : : : : : : : : : : : : : : : : 1707.28 Schematic of microphone based on Faraday's law of induction. 1717.29 Exercise 7.14. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1717.30 Exercise 7.15. : : : : : : : : : : : : : : : : : : : : : : : : : : : 1727.31 Exercise 7.18. : : : : : : : : : : : : : : : : : : : : : : : : : : : 172
8.1 Electric Field around charged ping-pong ball. : : : : : : : : : 1748.2 Oscillating charged ball. : : : : : : : : : : : : : : : : : : : : : 174
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8.3 Generation of electromagnetic waves at two di�erent frequen-cies. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 175
8.4 Spectrum of electromagnetic waves. : : : : : : : : : : : : : : : 1758.5 Electromagnetic waves are transverse waves with oscillating
electric and magnetic �elds. : : : : : : : : : : : : : : : : : : : 1768.6 Production of electromagnetic waves by oscillating electrons
in antenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1768.7 Generation of electric and magnetic �elds by antenna. : : : : 1778.8 Production of electromagnetic waves by antenna. : : : : : : : 1778.9 Some examples of modulation. : : : : : : : : : : : : : : : : : 1788.10 Amplitude modulation. : : : : : : : : : : : : : : : : : : : : : 1788.11 Carrier and audio signals broadcast by two stations. : : : : : 1798.12 Spectrum of an AM carrier at frequency f when modulated
by audio signal. : : : : : : : : : : : : : : : : : : : : : : : : : : 1798.13 Audio frequencies modulating carrier. : : : : : : : : : : : : : 1808.14 Spectrum of frequencies on carrier for audio frequencies up
to 5 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1808.15 Spectrum of frequencies due to modulation of carrier. : : : : 1818.16 Frequency modulation (FM). : : : : : : : : : : : : : : : : : : 1818.17 A low frequency and a high frequency audio signal frequency
modulating a carrier. : : : : : : : : : : : : : : : : : : : : : : : 1828.18 A loud and a quiet audio signal frequency modulating a carrier.1838.19 Action of limiter in FM. : : : : : : : : : : : : : : : : : : : : : 1848.20 Pre-emphasis in FM broadcasting. : : : : : : : : : : : : : : : 1848.21 Information brought to tuner on carrier. : : : : : : : : : : : : 1858.22 De-emphasis of audio information to reduce high frequency
noise. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1858.23 Elements of radio communications. : : : : : : : : : : : : : : : 1868.24 Superheterodyne receiver. : : : : : : : : : : : : : : : : : : : : 1868.25 Processing part of AM signal with a simple diode and �lters. 1868.26 Audio information which will modulate carrier in stereo broad-
casting. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1878.27 Alternating current in antenna produces electromagnetic wave.1888.28 Electric �eld around charged antenna wires is similar to that
between charged capacitor plates. : : : : : : : : : : : : : : : : 1898.29 Magnetic �elds around a wire and antenna with current. : : : 1898.30 Development of a standing wave on antenna. : : : : : : : : : 1908.31 Comparison of standing wave on antenna to that of a string. 191
xi
8.32 Radiation pattern of electric �eld around half-wave dipoleantenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 192
8.33 Polar graph representation of radiation pattern around half-wave dipolar antenna. : : : : : : : : : : : : : : : : : : : : : : 192
8.34 Basic elements of a grounded vertical antenna. : : : : : : : : 1938.35 Quarter-wave antenna. : : : : : : : : : : : : : : : : : : : : : : 1938.36 Total antenna length is made shorter by inserting a coil in
series. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1948.37 When the electric �eld of radio wave is vertical, the receiving
antenna should also be vertical. : : : : : : : : : : : : : : : : : 1958.38 Loop antenna detects the magnetic �eld part of radio wave. : 1958.39 Two common loop antennas. : : : : : : : : : : : : : : : : : : 1968.40 Vertically polarized radio wave. : : : : : : : : : : : : : : : : : 1968.41 Horizontally polarized radio wave. : : : : : : : : : : : : : : : 1978.42 Broadcasting with circular polarization. : : : : : : : : : : : : 1978.43 Low frequency ground wave follows curvature of earth. : : : : 1988.44 Direct (line-of-sight) mode of propagation. : : : : : : : : : : : 1988.45 Earth's ionosphere layers. : : : : : : : : : : : : : : : : : : : : 1998.46 Sky wave world communications. : : : : : : : : : : : : : : : : 1998.47 Two-hop transmission of radio wave using ionosphere. : : : : 2008.48 Communication using a satellite. : : : : : : : : : : : : : : : : 2008.49 Selectivity relates to how well alternate channels are rejected. 2018.50 Direct and re ected waves from a broadcasting station. : : : 2018.51 Capture ratio in tuner. : : : : : : : : : : : : : : : : : : : : : : 201
9.1 Record with grooves representing mechanically engraved waves.2039.2 Phono playback systems. : : : : : : : : : : : : : : : : : : : : : 2049.3 Stereo with only one stylus. : : : : : : : : : : : : : : : : : : : 2059.4 A stereo moving magnet phono cartridge. : : : : : : : : : : : 2069.5 Unmagnetized and magnetized magnetic material. : : : : : : 2069.6 Magnetic �eld produced by a coil when current ows through
it. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2079.7 Alignment of domains in a magnetic material. : : : : : : : : : 2089.8 Behavior of magnetic material in a coil whose current is in-
creased and decreased to zero. : : : : : : : : : : : : : : : : : : 2099.9 Memory is destroyed by reversed current in coil. : : : : : : : 2109.10 Hysteresis curve of magnetic material. : : : : : : : : : : : : : 2119.11 Groups of magnetic materials. : : : : : : : : : : : : : : : : : : 2129.12 Side and top views of magnetic tape. : : : : : : : : : : : : : : 213
xii
9.13 Magnetic particle of gamma { Iron (III) Oxide as used on tapes.2139.14 Recording head aligning magnetic domains on tape. : : : : : 2149.15 Analog recording on a magnetic tape. : : : : : : : : : : : : : 2159.16 Recorded information on magnetic tape. : : : : : : : : : : : : 2169.17 Playback head for reading information on a tape. : : : : : : : 2169.18 Playback head reading signals. : : : : : : : : : : : : : : : : : 2169.19 Order of heads on a tape deck. : : : : : : : : : : : : : : : : : 2179.20 Recording on material with magnetic hysteresis. : : : : : : : 2179.21 Recording a signal on a tape. : : : : : : : : : : : : : : : : : : 2189.22 Ideal magnetic characteristics for tape | linear behavior. : : 2199.23 Useful region on hysteresis curve for magnetic recording. : : : 2209.24 Recording on magnetic tape with bias. : : : : : : : : : : : : : 2219.25 Details of heads for magnetic recording. : : : : : : : : : : : : 2229.26 Frequency dependence of output from playback head. : : : : 2229.27 Output from playback head as a function of frequency for
various gap sizes and tape speeds. : : : : : : : : : : : : : : : 2239.28 Equalization in playback. : : : : : : : : : : : : : : : : : : : : 2239.29 Equalization in recording. : : : : : : : : : : : : : : : : : : : : 2249.30 Typical musical spectrum. : : : : : : : : : : : : : : : : : : : : 2249.31 Frequency response at di�erent recording levels. : : : : : : : : 2259.32 Exercise 9.4. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 225
10.1 Sound wave and its analog representation as a voltage. : : : : 22710.2 Grooves on a record representing analog signals. : : : : : : : 22810.3 Distortion of analog signal by dirt stuck between playback
head and tape. : : : : : : : : : : : : : : : : : : : : : : : : : : 22910.4 Original number 2 and worn out number 2; basic information
is not lost when number is worn out. : : : : : : : : : : : : : : 22910.5 (a) Analog signal, decimal scale (b) Analog signal, binary scale.23010.6 20 Hz wave will get more samples per wave than a 200 Hz wave.23010.7 Aliasing due to inadequate sampling rate. : : : : : : : : : : : 23110.8 Audio spectrum and sideband frequencies due to sampling. : 23210.9 Sample and hold of a signal for digitizing. : : : : : : : : : : : 23310.10 Multiplexing of left and right channels. : : : : : : : : : : : : 23310.11 Digitizing a signal. : : : : : : : : : : : : : : : : : : : : : : : : 23410.12 Output of D-A converter. : : : : : : : : : : : : : : : : : : : : 23410.13 Output of low-pass �lter. : : : : : : : : : : : : : : : : : : : : 23510.14 Main features of playback of digital signal. : : : : : : : : : : 23510.15 Details of information on a CD. : : : : : : : : : : : : : : : : 236
xiii
10.16 Interference between light beam re ected from pit and from at. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 237
10.17 Focusing action of a laser beam by lens. : : : : : : : : : : : : 23710.18 Reduced e�ect of surface defect on CD. : : : : : : : : : : : : 23810.19 Laser spot focused on disc data. : : : : : : : : : : : : : : : : 23910.20 Three-beam detection; one for read-out and two beams for
tracking. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 24010.21 Randomly polarized beam and plane-polarized beam. : : : : 24110.22 Path of laser beam and role of its polarization. : : : : : : : : 24210.23 Coherent and incoherent beams of light. : : : : : : : : : : : : 24310.24 Semiconductor laser. : : : : : : : : : : : : : : : : : : : : : : : 24410.25 E�ect of 2-times and 4-times oversampling. : : : : : : : : : : 24510.26 Shock-proof memory in mini-disc. : : : : : : : : : : : : : : : 246
11.1 Magnetic digital signals recorded vertically on a mini disc. : : 24811.2 Recording digital signals on a mini disc. : : : : : : : : : : : : 24811.3 Kerr e�ect: plane of polarization of light beam rotates upon
re ection from a magnetized surface. : : : : : : : : : : : : : : 24911.4 Read-out of digital information using Kerr e�ect. Magnetic
�eld direction a�ects plane of polarization of re ected laserbeam. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 249
11.5 Di�erence in read-out between pre-recorded and recordablemini-discs. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 250
11.6 Section of a recordable mini disc. : : : : : : : : : : : : : : : : 25111.7 Layered structure of recordable mini disc. : : : : : : : : : : : 25111.8 Track pattern in DCC tape. : : : : : : : : : : : : : : : : : : : 25211.9 The playback head reads only a portion of the recorded track. 25211.10 Threshold of hearing curve. : : : : : : : : : : : : : : : : : : : 25211.11 Sounds which will be recorded by PASC and masking of quiet
passages. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 25311.12 Representation of digital signal on magnetic tape. : : : : : : 25311.13 Helical recording with rotating heads. : : : : : : : : : : : : : 25411.14 Tape contact to rotating head. : : : : : : : : : : : : : : : : : 25511.15 Time compression to reduce wrap angle. : : : : : : : : : : : 25611.16 Guard band between tracks on analog tape reduces cross-talk.25711.17 Azimuthal recording. : : : : : : : : : : : : : : : : : : : : : : 25711.18 Digital information on magnetic tape recorded longitudinally. 25811.19 Arrangement of signals on a tape. : : : : : : : : : : : : : : : 25911.20 Exercise 11.7. : : : : : : : : : : : : : : : : : : : : : : : : : : 259
xiv
12.1 Sources of heating in hi-� due to mechanical friction and elec-trical \friction". : : : : : : : : : : : : : : : : : : : : : : : : : : 261
12.2 Electrical \friction" causes heating in ampli�er componentsand voice coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : 262
12.3 Two types of thermometers: alcohol expansion thermometerand gas thermometer. : : : : : : : : : : : : : : : : : : : : : : 263
12.4 Temperature dependence of electric resistance of a semicon-ductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 264
12.5 Basic circuit for resistance thermometer. : : : : : : : : : : : : 26412.6 Heating of spot on mini-disc for recording. : : : : : : : : : : : 26512.7 Heat conduction along a bar between a hot body and a cold
one. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 26512.8 Thermal resistance depends on length of heat conductor. : : : 26612.9 Thermal resistance depends inversely on cross-sectional area
of heat conductor. : : : : : : : : : : : : : : : : : : : : : : : : 26712.10 Transfer of heat in air by convection. : : : : : : : : : : : : : 26812.11 Object at temperature T emits electromagnetic waves. : : : 26812.12 Thermal expansion of an object when heated. : : : : : : : : 26912.13 Bimetallic strip and its behavior when heated or cooled. : : : 26912.14 Mounting of transistor and diode on heat sink to transfer
heat away from devices by heat conduction. : : : : : : : : : : 27012.15 Heat removal by convection and radiation. : : : : : : : : : : 27112.16 Action of circuit-breaker when too hot. : : : : : : : : : : : : 27112.17 Thermo-magnetic recording on mini-Disc. : : : : : : : : : : : 272
13.1 Speed of tape past recording head. : : : : : : : : : : : : : : : 27413.2 Time for a radio wave to go around the Earth at the equator. 27413.3 Speed of a recorded signal is the same at X and at Y; their
velocities are di�erent. : : : : : : : : : : : : : : : : : : : : : : 27513.4 Force on voice coil giving it a push or a pull depending on
direction of current in voice coil. : : : : : : : : : : : : : : : : 27613.5 Force on tape by capstan-pinch roller. : : : : : : : : : : : : : 27713.6 Static friction-force pulling on tape. : : : : : : : : : : : : : : 27713.7 Releasing a CD from its case by applying a pressure on the
clips with a �nger. : : : : : : : : : : : : : : : : : : : : : : : : 27813.8 Inertia of a tweeter is less than that of a woofer. : : : : : : : 27913.9 Outer ear; ear drum's inertia limits response at frequencies
above 20 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : 280
xv
13.10 Adjusted weight in cartridge for helping the stylus to trackthe groove in phono record. : : : : : : : : : : : : : : : : : : : 280
13.11 Force of clamped magnet on a voice coil accelerates diaphragmin loudspeaker. Force of clamped magnet on focus coil accel-erates focus lens in CD player. : : : : : : : : : : : : : : : : : 281
13.12 Re ection of a pulse on a string clamped at wall and itsinversion. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 282
13.13 Force on voice coil and force on magnet. : : : : : : : : : : : 28313.14 Waves recorded on a phono record and a CD. : : : : : : : : : 28413.15 Distances covered along outer track and inner track on a
phono record. : : : : : : : : : : : : : : : : : : : : : : : : : : : 28513.16 Frequency of rotation of a CD is made higher near the inner
edge and lower near the outer edge to maintain constant linearspeed on a tracks. : : : : : : : : : : : : : : : : : : : : : : : : 286
13.17 Rotation of drum head relative to magnetic tape in DAT. : : 28613.18 When same force is applied to the CD case lid, it is easier to
open the lid near the edge because torque is larger there. : : 28713.19 For the same force exerted on lid, the torque is larger in B
than in A. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 28813.20 Moment of inertia of a CD is larger than that of a mini-Disc. 288
xvi
Chapter 1
Introduction to Hi-Fi
1
CHAPTER 1. INTRODUCTION TO HI-FI 2
R
L
Playback Speakers
R
L
Record
Microphone
Microphone
Figure 1.1: Stereo process in recording and playback.
CHAPTER 1. INTRODUCTION TO HI-FI 3
Center Speaker
Stereo Left
Stereo Right
Surround Right
Surround Left
Figure 1.2: Surround sound reproduction of audio information.
Stereo
Left
Right
Store (Record)or
Transmit
Sourcesof
Sound
Left
Right
Stereo
Figure 1.3: Storage or transmission of sound in stereo.
CHAPTER 1. INTRODUCTION TO HI-FI 4
Right
Left
Right
Left
PlaybackSources
ofSound
Figure 1.4: Playback process in stereo.
+
=+
Tuner
Pre-Amplifier
PowerAmplifier
Receiver
Figure 1.5: Elements of a receiver.
CHAPTER 1. INTRODUCTION TO HI-FI 5
Receiver
Antenna
Phono
CD
Tape Deck
DAT
Figure 1.6: Example of basic connections to a receiver.
=+
Pre-Amplifier
PowerAmplifier
Integrated
Amplifier
Figure 1.7: Elements of an integrated ampli�er.
CHAPTER 1. INTRODUCTION TO HI-FI 6
Tuner
CD
Tape Deck
Phono
DAT
Antenna
Integrated Amplifier
Figure 1.8: Connections to an integrated ampli�er.
+
Separate components
Pre-AmpPower
Amplifier
Figure 1.9: All separate approach.
CHAPTER 1. INTRODUCTION TO HI-FI 7
Tuner
CD
Tape Deck
Phono
DAT
Pre-AmpPower
Amplifier
Antenna
Figure 1.10: Connections in all-separate approach.
CHAPTER 1. INTRODUCTION TO HI-FI 8
VCR
AudioInput
AudioOutput
VideoA/V Receiver VCR
L RStereo SpeakerOutput
VideoMonitor
Figure 1.11: Basic A/V System.
CHAPTER 1. INTRODUCTION TO HI-FI 9
VCR
AudioInput
AudioOutput
VideoA/V Receiver VCR
L R
VideoMonitor
Stereo SpeakerOutput
Surround SpeakerOutput
L R
Figure 1.12: A/V receiver driving a surround-sound system.
CHAPTER 1. INTRODUCTION TO HI-FI 10
Out forRecording
In fromTape Deck
SelectorSwitch
Out
In Out
Tape Deck
Tone ControlsTapeMonitorSwitch
Inputs
InOut
Figure 1.13: Details of the tape monitor switch when listening to a soundsource with available tape recording.
CHAPTER 1. INTRODUCTION TO HI-FI 11
Out forRecording
In fromTape Deck
Out
In Out
Tape Deck
Tone ControlsTapeMonitorSwitch
SelectorSwitch
Inputs
In
Out
Figure 1.14: Listening to a tape; tape switch in.
CHAPTER 1. INTRODUCTION TO HI-FI 12
R
A/V Receiver
TV
VCR
Center Channel Speaker
Video Audio
Video
Left SurroundSpeaker
Right SurroundSpeaker
Left Front
Speaker
Right Front
Speaker
Figure 1.15: A/V receiver with Dolby Pro Logic processor.
CHAPTER 1. INTRODUCTION TO HI-FI 13
A
Time
B
Time
C
Time
D
Time
E
Time
F
Time
G
Time
Amplitudeof
Signal
Amplitudeof
Signal
Amplitudeof
Signal
Figure 1.16: Various wave forms.
Chapter 2
Waves
14
CHAPTER 2. WAVES 15
Figure 2.1: Phono record and an enlarged groove showing engraved waverepresenting sound.
Distance
Displacement up
Displacement down
No Waves Waves
EquilibriumPosition
Figure 2.2: Simpli�ed picture of a water wave; displaced water as a functionof position.
CHAPTER 2. WAVES 16
Distance
Displacement up
Displacement down
1 Wave
Figure 2.3: Details of one wave as a function of position.
Displacement
Large Amplitude Small Amplitude
Distance
Figure 2.4: Large and small amplitude waves.
CHAPTER 2. WAVES 17
Displacementfrom
EquilibriumTime
+
-
Figure 2.5: Time dependence of displacement of a point on a water wave.
Time
+
-1 Period
Displacement
Figure 2.6: Displacement as a function of time; time required to completeone wave.
CHAPTER 2. WAVES 18
Clamp Clamp
String
Figure 2.7: Transverse wave on a string.
Figure 2.8: Longitudinal waves along a solid bar.
Position
Wave 1 Wave 2 Result
+ =Position Position
Figure 2.9: Addition of two waves.
CHAPTER 2. WAVES 19
No SoundSound
Air
Bell Jar
Vacuum
Figure 2.10: Sound requires a medium in which to propagate; in a vacuumthere is no sound propagation.
Direct Radiator Speaker
Diaphragm
Diaphragm
Drum
Figure 2.11: Direct radiator speaker can move air like a drumhead.
CHAPTER 2. WAVES 20
Speaker
Increase in Pressure = Condensation
Motion
SpeakerAir at Atmospheric Pressure
≈ 14.7 lbs./sq.in.
Figure 2.12: Generation of sound by loudspeaker.
CHAPTER 2. WAVES 21
Rarefaction Condensation
Equilibrium Pressureat ≈ 14.7 lbs./sq.in.
1 Wave
Pressure Change
Speaker Motion
Motion
Figure 2.13: Disturbances created by loudspeaker; pressure changes causesound.
DistanceEquilibriumAir Pressure
Air PressureIncrease
VibratingSpeaker
Air PressureDecrease
Louder Sound
Figure 2.14: Representation of sound created by a loudspeaker.
CHAPTER 2. WAVES 22
Wave XWave Y
Distance Distance
Amplitude Amplitude
0
1
2
-1
-2
0
1
2
-1
-2
Figure 2.15: Wave Y has 4 times the power of wave X, but their amplitudesdi�er only by a factor of 2.
Obstacle
Reflected Wave
Incoming Wave
Normal
Angle of Incidence
Angle of Reflection
Figure 2.16: Re ection of a wave by an obstacle or a di�erent medium.
CHAPTER 2. WAVES 23
Sound Produced
Time0
SoundPower
Speaker producesa Pulse of Sound
Figure 2.17: Speaker producing a pulse of sound in a hall.
CHAPTER 2. WAVES 24
Sound Produced
Time0
Direct
Reflected
Reflected
Direct
Amountof
Sound
Reverberant Sound
Figure 2.18: Paths of direct and re ected sound in a hall.
CHAPTER 2. WAVES 25
Reflected Sound
(Reverberant)
Direct Sound
Figure 2.19: Direct and reverberant sound in a hall.
CHAPTER 2. WAVES 26
Amountof
Sound
Source
Direct
Reverberant
About 6 meters from Stage
Distance from Source
Figure 2.20: Direct and reverberant sound contributions to sound in a hall.
CHAPTER 2. WAVES 27
1 2 3 4
Figure 2.21: Sound radiated by a speaker; as one moves away the intensitydecreases.
CHAPTER 2. WAVES 28
1
2
Figure 2.22: Sound intensity through surface 2 is di�erent from that of 1.
CHAPTER 2. WAVES 29
At Rest
Relative Motion
Figure 2.23: Observer and source at rest and in relative motion.
CHAPTER 2. WAVES 30
Speaker moving toward Listener
Speaker moving away from Listener
Increase in Frequency heard by Listener
100 Hz Signal
Decrease in Frequency heard by Listener
1000 Hz Signal
Figure 2.24: Doppler E�ect produced by speaker producing simultaneously100 Hz and 1,000 Hz sound waves.
CHAPTER 2. WAVES 31
Hot Air
Cold Air
IncomingSoundWave
Figure 2.25: Sound wave in cold air entering hot air.
Hot Air
Cold Air
Normal
Figure 2.26: Refraction of a sound wave.
CHAPTER 2. WAVES 32
Hot Air Normal
Cold Air
Critical Angle
Figure 2.27: Above a critical angle of incidence there is only re ection.
CHAPTER 2. WAVES 33
Air
Plastic
Sound Waves
Figure 2.28: Sound travels in a curved hollow plastic tube by multiple re- ections.
CHAPTER 2. WAVES 34
TimeDisplacement
Figure 2.29: Sound wave produced by a musical group; a complex wave.
Time
Displacement
0
Figure 2.30: Simple sine waveform.
CHAPTER 2. WAVES 35
Timeor
Position360˚
360˚
180˚180˚
90˚
90˚
270˚
270˚
Figure 2.31: Comparison between one full wave and one rotation of a circle.
+ =Time
orPosition
Disturbance Disturbance Disturbance
0 0 0Time
orPosition
Timeor
Position
Figure 2.32: Addition of two waves.
+ =Position Position Position
Displacement Displacement Displacement
0 0 0
Figure 2.33: Addition of two waves out of phase by 180 degrees.
CHAPTER 2. WAVES 36
In Phase
Figure 2.34: Constructive interference.
CHAPTER 2. WAVES 37
Out of Phase
Figure 2.35: Destructive interference.
CHAPTER 2. WAVES 38
Figure 2.36: Obstacle with aperture receiving high frequency waves.
CHAPTER 2. WAVES 39
Figure 2.37: Low frequency behavior of obstacle and aperture.
CHAPTER 2. WAVES 40
Figure 2.38: Comparison of di�raction behavior of a room with opening anda loudspeaker.
CHAPTER 2. WAVES 41
Low Frequencies
High Frequencies
Figure 2.39: Dispersion characteristics of a speaker.
Incident Wave
Reflected Wave
Result
Figure 2.40: Standing wave produced by incident and re ected waves.
CHAPTER 2. WAVES 42
Figure 2.41: Simplest possible standing wave on a string.
CHAPTER 2. WAVES 43
1/2 Wave
Figure 2.42: Simplest standing wave on a string during one cycle.
Node Antinode Node Antinode NodeDisplacement:
Figure 2.43: Second harmonic on a string showing position of nodes andantinodes.
Third Harmonic
Figure 2.44: Third harmonic on a string clamped at both ends.
CHAPTER 2. WAVES 44
Or
Figure 2.45: Setting up a standing wave in a tube.
CHAPTER 2. WAVES 45
1/2 Wave
DisplacementAntinode
DisplacementAntinode
Node
Figure 2.46: Simplest standing wave in a tube open at both ends.
Second Harmonic
Figure 2.47: Second harmonic in tube open at both ends.
1/2 Wave
1 Meter
Figure 2.48: Fundamental in a tube.
CHAPTER 2. WAVES 46
Figure 2.49: Tube open at one end excited by a tuning fork.
1/4 Wave
DisplacementAntinode
DisplacementNode
Figure 2.50: Fundamental in tube open at one end.
CHAPTER 2. WAVES 47
3/4 Wave
1/4 Wave 1/4 Wave 1/4 Wave
Figure 2.51: Next more complicated standing wave; the third harmonic.
Fifth Harmonic
Figure 2.52: Fifth harmonic.
1/4 Wave
1 Meter
Figure 2.53: Standing wave in a tube 1 meter long; fundamental.
CHAPTER 2. WAVES 48
Figure 2.54: Tube closed at both ends.
1/2 Wave
DisplacementNode
DisplacementNode
Antinode
Figure 2.55: Fundamental of a tube closed at both ends.
CHAPTER 2. WAVES 49
z
x
y1/2 Wave
1/2 Wave
1/2 Wave
Figure 2.56: Room where independent standing waves can be set up in thex, y, and z directions.
CHAPTER 2. WAVES 50
Figure 2.57: A drumhead �xed at its edges and its fundamental mode ofvibration.
CHAPTER 2. WAVES 51
Figure 2.58: Overtone on a drumhead.
Figure 2.59: Standing wave pattern on a Chladni plate.
CHAPTER 2. WAVES 52
+ =
100 Hz 400 Hz
Complex Wave
Figure 2.60: Complex wave created by the superposition of a 100 Hz funda-mental and its fourth harmonic.
CHAPTER 2. WAVES 53
Figure 2.61: Violin string plucked by a �nger and producing all sorts ofharmonics.
CHAPTER 2. WAVES 54
TimeDisplacement
Figure 2.62: Complex wave generated by plucking string.
CHAPTER 2. WAVES 55
Amplitude
Time
Frequency Relative Amplitude
3f 1/3
f 1
5f 1/5
nf 1/n
... ...
...
n = odd integer
Figure 2.63: Square wave; it is made up of many harmonics.
CHAPTER 2. WAVES 56
RelativeAmplitude
Harmonics
1.0
0.5
0
1 2 3 4 5 6 7
Figure 2.64: Spectrum of a square wave.
CHAPTER 2. WAVES 57
Amplitude
Time
Frequency Relative Amplitude
2f 1/2
3f 1/3
f 1
4f 1/4
5f 1/5
nf 1/n
... ... ...
n = integer
Figure 2.65: Sawtooth wave and its harmonic content.
CHAPTER 2. WAVES 58
RelativeAmplitude
Harmonics
1.0
0.5
0
1 2 3 4 5 6 7 8
Figure 2.66: Spectrum of a sawtooth wave.
CHAPTER 2. WAVES 59
Figure 2.67: A string bowed at its middle and harmonics which are excited.
CHAPTER 2. WAVES 60
Hammer
Figure 2.68: String on a piano struck by hammer at a distance 1/10 thestring length from one end.
Frequency
Amplitude
Natural Frequency
Figure 2.69: Vibrations of an object at di�erent excitation frequencies.
CHAPTER 2. WAVES 61
Undamped Damped
Oil
Figure 2.70: Oscillations of a mass on a spring, undamped and dampedwhen submersed in oil.
Ping Pong Ball
Figure 2.71: Resonance of wine glass excited by sound.
CHAPTER 2. WAVES 62
F1
F2
Time
Time
Time
Resultant
Figure 2.72: Beats caused by the combination of two waves with slightlydi�erent frequencies.
Chapter 3
Decibels
63
CHAPTER 3. DECIBELS 64
dB
Figure 3.1: Decibel meter.
Volume-70 dB
0 dB
Receiver
Figure 3.2: Receiver with volume control marked in dB.
0
20
40
60
80
100
120
140
20 100 1,000 10,000
Frequency (Hz)
Sou
nd P
ress
ure
Leve
l (dB
)
Range of Human Hearing
Threshold of Hearing
Threshold of Pain
Figure 3.3: Response of human ears at the threshold of hearing.
CHAPTER 3. DECIBELS 65
Frequency (Hz)
So
un
d P
ress
ure
Lev
el (
dB
)
20 31.5 63 125 250 500 1000 2000 4000 8000 16000 20000
140
120
100
80
60
40
20
0Threshold of Hearing
10 dB20 dB
30 dB
50 dB
70 dB
90 dB
110 dB
130 dB
40 dB
60 dB
80 dB
100 dB
120 dB
Figure 3.4: Response of human ears for various sound levels: Fletcher-Munson curves.
Outer Ear Tube closed at one End
Figure 3.5: Outer ear approximated by a tube closed at one end.
CHAPTER 3. DECIBELS 66
Speaker Sound Level
Meter
(dB Meter)
Aux
Receiver
Audio
Signal
Generator
dB
Figure 3.6: Measuring the frequency response of a speaker.
Sound Level (dB)
Frequency
90
70
20 Hz 1,000 Hz 20,000 Hz
Ideal
Real
Figure 3.7: Frequency response of a speaker.
Chapter 4
Loudspeakers
67
CHAPTER 4. LOUDSPEAKERS 68
ElectricalSignalInput
Loudspeaker
SoundOutput
Figure 4.1: Role of loudspeaker.
CHAPTER 4. LOUDSPEAKERS 69
Amplitude
FrequencyHarmonics1 2 3 4 5 6 7
Amplitude
Frequency
ResultantAmplitude
FrequencyHarmonics1 2 3 4 5 6 7
Spectrum of an Input Tone
Frequency Response of Speaker
Sound from Speaker
+
Figure 4.2: Distortion of spectrum of original waveform by non- at fre-quency response of speaker.
CHAPTER 4. LOUDSPEAKERS 70
Low Frequencies
High Frequencies
Figure 4.3: Dispersion properties of speakers.
CHAPTER 4. LOUDSPEAKERS 71
O1
2
Figure 4.4: Two low frequency waves from speaker arriving at O.
CHAPTER 4. LOUDSPEAKERS 72
O
1
2
Figure 4.5: Two high frequency waves from speaker arriving at O.
CHAPTER 4. LOUDSPEAKERS 73
O
1
2
2 1/2 Waves
Figure 4.6: Details of waves 2 and 1 at high frequencies.
CHAPTER 4. LOUDSPEAKERS 74
Lows
Middles
Highs
"On Axis" All Frequencies
are heard.
"Off Axis" High Frequencies are
almost not heard.
Speaker
Figure 4.7: Sound dispersion of a driver as the frequency is increased.
CHAPTER 4. LOUDSPEAKERS 75
Woofer
TotalSoundOutput
Midrange
TotalSoundOutput
Tweeter
Frequency
TotalSoundOutput
Cross-over Frequencies
Frequency
Frequency
Figure 4.8: Division of audio spectrum for a three-way loudspeaker.
CHAPTER 4. LOUDSPEAKERS 76
Woofer Midrange Tweeter
Frequency
TotalSoundOutput
3-Way Speaker
500 Hz 5000 Hz
Figure 4.9: Net e�ect of subdividing the whole audio range into three sec-tions.
Cross-over Frequency
Woofer Tweeter
Frequency
SoundOutput
Figure 4.10: Subdivision of audio spectrum in a two-way system.
CHAPTER 4. LOUDSPEAKERS 77
Displacement Displacement
A B
Figure 4.11: Amount of sound produced depends on volume displacement.A is louder than B.
CHAPTER 4. LOUDSPEAKERS 78
Displacement
Displacement
Figure 4.12: To produce same amount of sound by both drivers at the samefrequency, the small one has to move through a larger distance than the bigone.
CHAPTER 4. LOUDSPEAKERS 79
Frequency0.0005
0.5
500
20 200 2000 20,000
Volume ofAir moved
3(cm )
Figure 4.13: Volume of air moved by loudspeaker as a function of frequencyto produce same loudness of sound.
CHAPTER 4. LOUDSPEAKERS 80
High Frequency
Low Frequency
Figure 4.14: Low frequency and high frequency simple pendulums doingdi�erent amounts of work per second for same amplitude of displacement.
ElectricalPower
In
SoundPower and
HeatDissipation
IN OUT
Figure 4.15: Balance between electrical power going to driver and the pro-duction of sound power and heat dissipation by driver.
CHAPTER 4. LOUDSPEAKERS 81
ElectricalPower
Input fromReceiver(80 Watts)
Loudspeaker
SoundOutput
(2 Watts)
Figure 4.16: Example of a loudspeaker whose e�ciency is less than 100%.
CHAPTER 4. LOUDSPEAKERS 82
Cone
Suspension
Magnet
Voice Coil
Spider
Basket
Figure 4.17: Basic cone speaker.
CHAPTER 4. LOUDSPEAKERS 83
Cone-shaped Diaphragm Flat Diaphragm
Figure 4.18: Comparison of cone-shape over at shape for mechanicalstrength when thin material is used.
CHAPTER 4. LOUDSPEAKERS 84
Diaphragm
Flexible Edge
Figure 4.19: Modeling of diaphragm action by mass-spring oscillating sys-tem.
CHAPTER 4. LOUDSPEAKERS 85
Side View Front View
12
3
1
2
3
Figure 4.20: Standing wave on diaphragm of driver.
Down
Down
Up
Up
Up
Up
Down
Down
N
A
N
A
N
N
A A
N
A
N
A
N
N
A A
N = NodeA = Antinode
Figure 4.21: Standing wave around rim of diaphragm.
CHAPTER 4. LOUDSPEAKERS 86
SoundPressure
(dB)
Frequency
Main Resonance
Standing Wave Resonances
Figure 4.22: Typical frequency response of a cone speaker.
Front Sound(In Phase)
Rear Sound(Out of Phase)
Rear Sound(Out of Phase)
Figure 4.23: Ba�e problem in cone driver.
CHAPTER 4. LOUDSPEAKERS 87
Figure 4.24: Front and rear of cone speakers are 180� out of phase.
CHAPTER 4. LOUDSPEAKERS 88
Baffle
Path = 1/2 Wave
Figure 4.25: Ba�e action.
Figure 4.26: Two possible approaches for trapping rear sound in a speakerby means of an enclosure.
CHAPTER 4. LOUDSPEAKERS 89
Frequency
Amplitude
With Enclosure
Without Enclosure
Resonant Frequency of Driver
Resonant Frequency of Driver + Enclosure
Frequency
Amplitude
With Enclosure
Without Enclosure
Resonant Frequency of Driver
Resonant Frequency of Driver + Enclosure
OR
Figure 4.27: E�ect of enclosure on frequency response of speaker.
CHAPTER 4. LOUDSPEAKERS 90
Cotton Wool
Figure 4.28: Reducing standing waves inside speaker enclosure.
CHAPTER 4. LOUDSPEAKERS 91
Port
Driver
Figure 4.29: Basic bass-re ex enclosure.
CHAPTER 4. LOUDSPEAKERS 92
Figure 4.30: Oscillating components of bass-re ex speaker.
CHAPTER 4. LOUDSPEAKERS 93
Frequency
Frequency
Frequency
+
Amplitude
Amplitude
ResultantAmplitude
Driver
Enclosure
Result
Figure 4.31: Splitting of original resonance into two new resonances in bass-re ex system.
CHAPTER 4. LOUDSPEAKERS 94
DriverAir in Enclosure
Air in Enclosure
Air in Enclosure
Air in Enclosure
Air in Enclosure
Out-of-PhaseMotion
In-PhaseMotion
Figure 4.32: Resonant behavior, in-phase and out-of-phase, motion ofstrongly coupled components of bass-re ex system.
CHAPTER 4. LOUDSPEAKERS 95
Driver
Airin
EnclosurePort
Figure 4.33: Coupled components of a bass-re ex speaker.
CHAPTER 4. LOUDSPEAKERS 96
PassiveRadiator
Driver
Figure 4.34: Bass-re ex speaker using a passive radiator over the port.
CHAPTER 4. LOUDSPEAKERS 97
Spring
Mass
Figure 4.35: Helmholtz resonator behaves like mass-spring system.
CHAPTER 4. LOUDSPEAKERS 98
Port Duct
Figure 4.36: Bass-re ex speaker using a port or a duct.
CHAPTER 4. LOUDSPEAKERS 99
Figure 4.37: Acoustic labyrinth enclosure.
CHAPTER 4. LOUDSPEAKERS 100
Driver + Small Enclosure
Frequency
Amplitude
Driver alone
Very LowResonant Frequency
Figure 4.38: Change of frequency response of speaker when a small enclosureis used.
CHAPTER 4. LOUDSPEAKERS 101
+Small Enlosure
Frequency
AmplitudeDriver + Small Enclosure
30 Hz
Frequency
Amplitude Driver alone
15 Hz
=
Large Compliance
Figure 4.39: E�ect of small enclosure on frequency response of driver.
CHAPTER 4. LOUDSPEAKERS 102
Figure 4.40: Transfer of energy from a bob to one of equal mass, and to oneof di�erent mass.
CHAPTER 4. LOUDSPEAKERS 103
AirChamber
Diaphragm
Throat
Mouth
Figure 4.41: A horn for matching vibrations of a light diaphragm to a largevolume of air.
Frequency
Cut-off Frequency
Amplitude
Figure 4.42: Low frequency response of a horn.
CHAPTER 4. LOUDSPEAKERS 104
Conical
Exponential
Hyperbolic
Parabolic
Figure 4.43: Some common horn shapes.
CHAPTER 4. LOUDSPEAKERS 105
Diaphragm
Figure 4.44: Folded horn.
CHAPTER 4. LOUDSPEAKERS 106
Figure 4.45: Two-way horn loudspeaker with bass-re ex enclosure.
CHAPTER 4. LOUDSPEAKERS 107
Loudspeaker
1/2 Wavelength
Figure 4.46: Standing wave set up in a room with maxima and minima insound pressure.
LoudspeakerDirect
Figure 4.47: Re ected waves by a wall appear to come from behind the wallsince it acts like a mirror.
CHAPTER 4. LOUDSPEAKERS 108
Lows
Highs
Middles
Highs
Lows
Middles
Lows
Figure 4.48: Stereo coverage in a room.
L
R
+_
+_ +
_
+_
Figure 4.49: Speaker phasing: speakers are in phase.
CHAPTER 4. LOUDSPEAKERS 109
L
R
+_
+_
+_
+_
Figure 4.50: Speaker phasing: speakers are out of phase.
Wall
Direct
Reflected Reflected
Figure 4.51: Geometry of a Bose 901 speaker.
CHAPTER 4. LOUDSPEAKERS 110
Frequency
Amplitude
Speaker
Frequency
Amplitude Equalizer
Frequency
ResultantAmplitude
Speaker
Figure 4.52: E�ect of equalizer on frequency response of Bose speakers.
CHAPTER 4. LOUDSPEAKERS 111
Wall
Figure 4.53: Bass horn in Klipsch horn speaker.
+12 dB
0 dB
-12 dB62Hz 250Hz 1kHz 4kHz 8kHz
Left Channel
Figure 4.54: Graphic equalizer.
Chapter 5
Electricity
112
CHAPTER 5. ELECTRICITY 113
N
N
Neutron
Proton
Electron
Electron
Figure 5.1: Example of an atom: a Helium atom.
CHAPTER 5. ELECTRICITY 114
Figure 5.2: Forces between charged objects; like charges repel and unlikecharges attract.
CHAPTER 5. ELECTRICITY 115
Figure 5.3: Charged ping-pong balls repelling each other.
Figure 5.4: Electric �eld produced by a charged object.
CHAPTER 5. ELECTRICITY 116
Figure 5.5: Electric �eld between two charged plates.
Output
Receiver
Left Right
Battery
Figure 5.6: Examples of voltage sources: a battery, the output of a receiver.
CHAPTER 5. ELECTRICITY 117
Plates
Sheet
Figure 5.7: Electrostatic speaker: basic principle and actual speaker.
Sheet
Plates
Figure 5.8: Simpli�ed version of an electrostatic speaker at equilibrium.
CHAPTER 5. ELECTRICITY 118
Figure 5.9: Push-pull action by two plates on charged sheet.
Plates
Diaphragm (Vibrating Sheet)
Spacers
Figure 5.10: An electrostatic speaker.
CHAPTER 5. ELECTRICITY 119
Si Ion
O Ion
Stress
Stress
2
Quartz
Figure 5.11: Some crystals under pressure produce positive and negativecharges on surface.
V V
V = 0
Figure 5.12: Dimensional changes of a piezoelectric ceramic when a voltageis applied.
CHAPTER 5. ELECTRICITY 120
V
V
Figure 5.13: Bending action of a double piezoelectric driver.
Bimorph
Cone
Figure 5.14: Pumping action of cone caused by bending of bimorph.
CHAPTER 5. ELECTRICITY 121
Diaphragm
Figure 5.15: Typical piezo horn.
Wire
Figure 5.16: Wire connected between two charged objects allows charges tobe transferred.
CHAPTER 5. ELECTRICITY 122
L
R
+_
+_
Figure 5.17: Flow of electric current from ampli�er to speaker.
Bound Electrons
Atom
Figure 5.18: Solid with atoms where electrons are tightly bound and whichdoes not conduct electricity under normal circumstances.
CHAPTER 5. ELECTRICITY 123
Electron
Figure 5.19: Motion of one electron in a conductor in the presence of anelectric �eld. Changes of direction are due to scattering.
CHAPTER 5. ELECTRICITY 124
ElectricalResistance
Temperature (˚K)0 100 200 300
Metal
Figure 5.20: Temperature dependence of the electrical resistance in a con-ductor.
ElectricalResistance
Temperature (˚K)0 100 200 300
Tc
Superconductor
Figure 5.21: Superconductivity at Tcbelow which the resistance is zero.
CHAPTER 5. ELECTRICITY 125
Water flowing in Pipe
Wire of Conductor
1
2
1
2
Figure 5.22: The resistance to current or to water ow increases as thelength of a conductor or pipe increases. Resistance of 2 is double that of 1.
Wire of Conductor Water flowing in Pipe
Figure 5.23: By increasing the cross-sectional area of a conductor, resistanceto current or water ow decreases.
CHAPTER 5. ELECTRICITY 126
Figure 5.24: Resistor with colored bands to specify its resistance value.
SiSi Si
Si Si
SiSi Si
Ga
SiSi Si
Si Si
SiSi Si
As
Extra Electron
Missing ElectronBonding
SiSi Si
SiSi Si
SiSi Si
= Hole
Figure 5.25: Pure silicon, silicon doped with arsenic, and silicon doped withgallium.
+
_
Amplifier VoltageSource
Simple Model
Resistance
Figure 5.26: Example of simple circuit.
CHAPTER 5. ELECTRICITY 127
Water Flow
Pump Resistance toWater Flow
Figure 5.27: Model using water for electric circuit.
CHAPTER 5. ELECTRICITY 128
Current
Time
DC
Current
Time
AC
Figure 5.28: Comparison between DC and AC current.
Time
Pressure Sound
Time
Voltage AC Signal
Figure 5.29: Representation of a sound wave by an AC electrical signal.
CHAPTER 5. ELECTRICITY 129
X Z
Y
Figure 5.30: Variable resistance between X and Y.
VoltageSource
Fuse
Fine Wire
Figure 5.31: Fuse to protect speaker.
L
R
+_
+_
Speaker 1 Speaker 2
Figure 5.32: Two speakers connected in series to one channel of ampli�er.
CHAPTER 5. ELECTRICITY 130
VoltageSource
Effective Resistor
Speaker 1 Speaker 2
Figure 5.33: Model of series circuit.
L
R
+_
+_
Figure 5.34: Parallel connection of two speakers to an ampli�er.
CHAPTER 5. ELECTRICITY 131
VoltageSource
Effective Resistor
Speaker 1
Speaker 2
Figure 5.35: Model of parallel connections.
HouseOutlet
120 V60 Hz
CDPlayer
Receiver Etc.Equalizer
Figure 5.36: Parallel connections of hi-� components to house electricaloutlet.
CHAPTER 5. ELECTRICITY 132
Mass
Suspension
• Compliance of Suspension
• Friction
• Mass of Cone
Figure 5.37: Response of cone speaker to a force.
CHAPTER 5. ELECTRICITY 133
Figure 5.38: Coil used to produce a magnetic �eld when a current owsthrough it. It has inductance.
CHAPTER 5. ELECTRICITY 134
20 Hz 20,000 HzFrequency
Impedancedue to
Inductance
Figure 5.39: Frequency dependence of impedance associated with induc-tance.
VoltageSource
VoltageSource
Figure 5.40: Charging of a capacitor.
CHAPTER 5. ELECTRICITY 135
VoltageSource
VoltageSource
Figure 5.41: Charging of a capacitor when polarity of voltage source isreversed.
20 Hz 20,000 HzFrequency
Impedancedue to
Capacitance
Figure 5.42: Frequency dependence of impedance due to capacitance.
CHAPTER 5. ELECTRICITY 136
Frequency
SoundOutput
Woofer
Inductance
In fromAmplifier
Woofer
Figure 5.43: Inductance in series with woofer prevents high frequencies fromreaching it.
Frequency
SoundOutput
Capacitance
In fromAmplifier
Tweeter
Tweeter
Figure 5.44: Capacitance in series with tweeter. It prevents low frequenciesfrom reaching it.
CHAPTER 5. ELECTRICITY 137
Frequency
SoundOutput
In fromAmplifier
Mid-range
Mid-range
Figure 5.45: Capacitance and inductance in series with mid-range speakerto prevent the high and low frequencies from reaching it.
Resonant FrequencyFrequency
Impedance
Figure 5.46: Impedance curve of driver.
Chapter 6
Ampli�ers
138
CHAPTER 6. AMPLIFIERS 139
WeakSignals
LargeSignals
AmplifierSources of
Audio Signals(CD, Tape, etc.)
Figure 6.1: Importance of ampli�er in hi-� system.
Source Commandfrom Audio Signals
SoundOutput
PowerSupply
Figure 6.2: Basic ampli�er.
CHAPTER 6. AMPLIFIERS 140
Source Command:
SoundOutput
More Current
PowerSupply
Figure 6.3: Ampli�er command for more current.
Source Command:
SoundOutput
Less Current
PowerSupply
Figure 6.4: Ampli�er command for less current.
CHAPTER 6. AMPLIFIERS 141
p-Type n-Type
Holes Electrons
Figure 6.5: Semiconductor junction.
No Current flow
BatteryBattery
p-type n-type p-type n-type
Figure 6.6: Reverse-biased semiconductor junction.
CHAPTER 6. AMPLIFIERS 142
Battery Battery
Current flows
p-type n-type p-type n-type
Figure 6.7: Forward-biased semiconductor junction.
Current
+Voltage-Voltage
Figure 6.8: Symbol for diodes and its characteristics.
Voltageacross
Resistor
InputVoltage
Diode
Figure 6.9: Recti�er action of a diode when an AC voltage is applied.
CHAPTER 6. AMPLIFIERS 143
n p n p n p
Emitter EmitterCollector Collector
BaseBase
Figure 6.10: Diagram of transistor and its circuit symbol for two possibilities.
Commandgoes in as
Current
(Control)PowerSupply
Current Flow
Water Flow
Control
Water Tank
Figure 6.11: Ampli�er action of transistor in a circuit compared to controlof water ow.
CHAPTER 6. AMPLIFIERS 144
Amplifier
Signal In
Signal Out
Figure 6.12: Function of an ampli�er.
Input
OutputAmplifier
+ Battery
- Battery
Inverting
Non-InvertingInput
Ground
Figure 6.13: Ampli�er integrated on a chip.
Input
OutputAmplifier
Rf
Rinput
Figure 6.14: Operational ampli�er with negative feedback.
CHAPTER 6. AMPLIFIERS 145
Input
OutputAmplifier
Rf
Rinput
Figure 6.15: Negative feedback corrects uctuations in gain.
Amplifier
Microphone
Speaker
Figure 6.16: Positive feedback in large hall with a mike and a loudspeakersystem driven by mike.
CHAPTER 6. AMPLIFIERS 146
Input
Output
Ground
Figure 6.17: Volume control.
Input
Output isMaximum Voltage
Ground
Ball atMaximum
Energydue to itsPosition
Input
Output isMinimum Voltage
Ground
Ball atMinimum Energy
due to itsPosition
Figure 6.18: Comparison of potentiometer action with energy of a ball on aladder.
CHAPTER 6. AMPLIFIERS 147
Bass Treble
Min Max Min Max
Figure 6.19: Bass and Treble controls.
CHAPTER 6. AMPLIFIERS 148
RelativeOutput
(dB)
+ 13
-13
Frequency
Min. Bass
Max. bass
Min. Treble
Max. Treble
1000 Hz20 Hz 20,000 Hz
MiddlePosition
Figure 6.20: E�ect on signal spectrum of Bass and Treble controls.
RelativeAmplitude
(dB)
Frequency20 Hz 20,000 Hz
Low, 6 dB/Octave
Low, 18 dB/Octave
High, 6 dB/Octave
High, 18 dB/Octave
Ideal Casewith no Filter
Figure 6.21: Action of LOW and HIGH �lters with 6 dB/octave attenuation,and also with 18 db/octave attenuation.
CHAPTER 6. AMPLIFIERS 149
Amplifier
Signal In
Signal Out
Extra Harmonics
f
Signal Outf
2f 3f
+ + + ... =
Figure 6.22: Harmonic distortion by ampli�er.
Linear
Non-linear
Output
Input
Figure 6.23: Non-linear gain of ampli�er.
CHAPTER 6. AMPLIFIERS 150
Signal In
Frequency f 1
Frequency f 2Amplifier
Signal Out
f 1
f 2
f 1 f 2-
f 1 f 2+
Figure 6.24: IM distortion in ampli�er.
Distortion(%)
Power Output
IM
THD
Power Rating of Amplifier
Figure 6.25: Distortion increases sharply about power rating of ampli�er.
CHAPTER 6. AMPLIFIERS 151
Signal In
Amplifier
Signal Out
Large THDdue to Clipping
Figure 6.26: Clipping of waveform by ampli�er at high output levels beyondthe rated value.
Signal In
Amplifier
Signal Out
Noise
Figure 6.27: E�ect of noise from ampli�er.
CHAPTER 6. AMPLIFIERS 152
RelativeOutput
(dB)
20 Hz 20,000 Hz
A
Frequency
RelativeOutput
(dB)
20 Hz 20,000 Hz
B
Frequency
Figure 6.28: Comparing 2 ampli�ers with the same specs. Even though theirspecs are the same, the ampli�ers will sound di�erent.
20 Hz 20,000 HzFrequency
0 dB Noise Level
A - weighted Measured Noise Level
Figure 6.29: A-weighted method of measuring noise.
Chapter 7
Electromagnetism
153
CHAPTER 7. ELECTROMAGNETISM 154
Current
Figure 7.1: E�ect of current in a wire on compasses around it.
North South
Figure 7.2: Bar magnet has a north pole and a south pole.
North South N S N S
Figure 7.3: Cutting a bar magnet produces shorter magnets each with itsown respective north and south poles.
CHAPTER 7. ELECTROMAGNETISM 155
N SN S
Current
Magnetic Field Magnetic Field
Figure 7.4: Magnetic dipole is the basic unit of magnetism.
Magnetic DomainIron Atom
Figure 7.5: Unmagnetized piece of iron.
CHAPTER 7. ELECTROMAGNETISM 156
N S
Magnet
Magnetized Iron
North South
Figure 7.6: Alignment of domains in a piece of iron by a bar magnet. Ironbecomes magnetized.
North South
Current
Figure 7.7: Magnetic �eld around a bar magnet and a wire carrying a cur-rent.
CHAPTER 7. ELECTROMAGNETISM 157
Single LoopMany Loops = Coil
Battery
Figure 7.8: Increasing the magnetic �eld produced by a current in a wire:by forming a loop, and by using many loops.
S
Power Supply
N
- +
Figure 7.9: An electromagnet.
CHAPTER 7. ELECTROMAGNETISM 158
S
Power Supply
N
- +
Figure 7.10: Determination of direction of magnetic �eld using �rst left-handrule.
North Pole
Current
S N
- +
Left Hand
Figure 7.11: Rule for determining direction of magnetic �eld in an electro-magnet.
CHAPTER 7. ELECTROMAGNETISM 159
Amplifier
Fixed Magnet
N SN S
Direction of Motion
Figure 7.12: First left-hand rule and how a cone speaker works.
Current
Force
N S
Figure 7.13: Force on wire carrying a current in a magnetic �eld.
CHAPTER 7. ELECTROMAGNETISM 160
Force
Current(Negative to Positive)
Magnetic Field(North to South)
Left Hand
Figure 7.14: The second left-hand rule showing direction of force on wirecarrying a current in a magnetic �eld.
CHAPTER 7. ELECTROMAGNETISM 161
Current
Zero Force
Magnetic Field
Current
Maximum Force
Magnetic Field
Figure 7.15: Direction of force depends on orientation of current with respectto magnetic �eld.
CHAPTER 7. ELECTROMAGNETISM 162
SSS
+
Magnet Poles
Magnet Poles
N NN
Figure 7.16: A Heil Speaker.
CHAPTER 7. ELECTROMAGNETISM 163
SMagnet Pole
NMagnet Pole
Force Force
Wire with Current
Figure 7.17: One set of folds in Heil speaker.
CHAPTER 7. ELECTROMAGNETISM 164
NS SN
SN NS
+
Magnet
Wire
Sheet
N S
Figure 7.18: Magnetic Planar Speaker.
CHAPTER 7. ELECTROMAGNETISM 165
NS S N
NS S N
Wire
Figure 7.19: Forces on diaphragm when current direction is as indicated.
N S
Figure 7.20: A bar magnet moving into a coil induces an electric current inthat coil.
CHAPTER 7. ELECTROMAGNETISM 166
N S
N S
N SN S
Figure 7.21: Induced current in coil by moving magnet.
CHAPTER 7. ELECTROMAGNETISM 167
N S
N S
Figure 7.22: Signi�cance of relative motion between magnet and coil.
N S
WRONG!!
Figure 7.23: Direction of induced current (wrong).
CHAPTER 7. ELECTROMAGNETISM 168
N S
CORRECT!!
Figure 7.24: Direction of induced current (correct).
CHAPTER 7. ELECTROMAGNETISM 169
Secondary CoilPrimary Coil
Core
Figure 7.25: Schematic of a transformer and its circuit symbol.
CHAPTER 7. ELECTROMAGNETISM 170
Secondary CoilPrimary Coil
Figure 7.26: Step-up transformer.
Secondary CoilPrimary Coil
Figure 7.27: Step-down transformer.
CHAPTER 7. ELECTROMAGNETISM 171
N S
Figure 7.28: Schematic of microphone based on Faraday's law of induction.
S N
Figure 7.29: Exercise 7.14.
CHAPTER 7. ELECTROMAGNETISM 172
NS
Stationary
+
Figure 7.30: Exercise 7.15.
SN
Figure 7.31: Exercise 7.18.
Chapter 8
Electromagnetic Waves and
Tuners
173
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 174
Figure 8.1: Electric Field around charged ping-pong ball.
Figure 8.2: Oscillating charged ball.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 175
Oscillating Charged CombHigh-frequency
Oscillating Electron
Figure 8.3: Generation of electromagnetic waves at two di�erent frequencies.
Radio Microwave Infrared Light Ultra-violet X-rays Gamma-rays
10 Hz6 10 Hz8 10 Hz12 10 Hz14 10 Hz15 10 Hz16 10 Hz18
Figure 8.4: Spectrum of electromagnetic waves.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 176
Electric Field
Magnetic Field
Direction of Travel
Figure 8.5: Electromagnetic waves are transverse waves with oscillating elec-tric and magnetic �elds.
Antenna
e-
e-
Waveform
VoltageSource
Antenna
e-
e-
Waveform
VoltageSource
Figure 8.6: Production of electromagnetic waves by oscillating electrons inantenna.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 177
MagneticField
ElectricField
Figure 8.7: Generation of electric and magnetic �elds by antenna.
Broadcasted Wave
Antenna
Figure 8.8: Production of electromagnetic waves by antenna.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 178
Test
Pressure Increase
Pressure Decrease
AmbientPressure
Writing
Painting a Picture Sound
Modulation:
Figure 8.9: Some examples of modulation.
Carrier
AudioSignal
Amplitude ModulatedCarrier Wave
Figure 8.10: Amplitude modulation.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 179
AudioSignal
AudioSignal
Station 1,000 kHz
ModulatedCarrier Wave
Station 1,400 kHz
Carrier
Carrier
ModulatedCarrier Wave
Figure 8.11: Carrier and audio signals broadcast by two stations.
Frequency
Amplitude
f - AudioFrequency
f + AudioFrequency
f
Carrier
Figure 8.12: Spectrum of an AM carrier at frequency f when modulated byaudio signal.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 180
Frequency
Amplitude
f
Carrier
AM Waves
Figure 8.13: Audio frequencies modulating carrier.
Frequency
RelativeAmplitude
ff - 5 kHz f + 5 kHz
Sideband Frequencies
Carrier
Figure 8.14: Spectrum of frequencies on carrier for audio frequencies up to5 kHz.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 181
Frequency
RelativeAmplitude
1000 kHz995 kHz 1005 kHz
1 Station Next Station
Carrier 1 Carrier 2
Figure 8.15: Spectrum of frequencies due to modulation of carrier.
AudioSignal
CarrierSignal
Frequency Modulated Carrier Wave
Amplitude does not change
Frequency changes
Figure 8.16: Frequency modulation (FM).
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 182
Low Frequency Audio
Carrier
High Frequency Audio
Carrier
Figure 8.17: A low frequency and a high frequency audio signal frequencymodulating a carrier.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 183
Quiet Audio
Carrier
Loud Audio
Carrier
Figure 8.18: A loud and a quiet audio signal frequency modulating a carrier.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 184
Spikes
Limiter
Figure 8.19: Action of limiter in FM.
RelativeAmplitude
(dB)
0
17
20 Hz 1 kHz 15 kHz
Audio Information
Frequency
Figure 8.20: Pre-emphasis in FM broadcasting.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 185
Relative Amplitude
(dB)
0
17
20 Hz 1 kHz 15 kHz
Audio Information
Frequency
Noise picked upin Atmosphere
Figure 8.21: Information brought to tuner on carrier.
RelativeAmplitude
(dB)
-17
0
20 Hz 1 kHz 15 kHz
Audio Information
Frequency
Noise
Figure 8.22: De-emphasis of audio information to reduce high frequencynoise.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 186
Tuner
Antenna
Amp
OutIn
Transmitter
Antenna
Figure 8.23: Elements of radio communications.
rfAmplifier Out
LocalOscillator
MixerIF
Amplifier
Rectifierand
Filter
Figure 8.24: Superheterodyne receiver.
Rectifier
I-F Signal A-F Signal
Filter
Figure 8.25: Processing part of AM signal with a simple diode and �lters.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 187
Frequency
Amplitude
50 15,000 19,000 23,000 38,000 53,000 Hz
Pilot Frequency
L+R L-R L-R
Figure 8.26: Audio information which will modulate carrier in stereo broad-casting.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 188
Electric Field
Antenna
At the same time ...
Magnetic Field
Figure 8.27: Alternating current in antenna produces electromagnetic wave.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 189
Antenna WiresCapacitor Plates
Electric Field Electric Field
Figure 8.28: Electric �eld around charged antenna wires is similar to thatbetween charged capacitor plates.
Current
Wire with Current
Antenna with Current
Magnetic Field
Current
Current
Figure 8.29: Magnetic �elds around a wire and antenna with current.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 190
Incident Current Wave
Reflected Current Wave
Resultant WaveCurrent
Figure 8.30: Development of a standing wave on antenna.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 191
Standing Wave on an Antenna
Standing Wave on a String
Current
Displacement
Figure 8.31: Comparison of standing wave on antenna to that of a string.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 192
Antenna Axis
Figure 8.32: Radiation pattern of electric �eld around half-wave dipole an-tenna.
Antenna
270˚
180˚
90˚
0˚
Radiation Lobe
Figure 8.33: Polar graph representation of radiation pattern around half-wave dipolar antenna.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 193
Current
Antenna
Co-axial Cable
to Electronics
1/4 Wave
Earth
1/4 Wave
Earth
Reflection
Electric Conductor
1/4 Wave
Figure 8.34: Basic elements of a grounded vertical antenna.
1/4 Wave
Ground Plane
Figure 8.35: Quarter-wave antenna.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 194
Reflected Part
Earth
Figure 8.36: Total antenna length is made shorter by inserting a coil inseries.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 195
Electric Field of Radio Wave Receiving
Antenna
Figure 8.37: When the electric �eld of radio wave is vertical, the receivingantenna should also be vertical.
Magnetic Field of Radio Wave
Tuner
Loop Antenna
Figure 8.38: Loop antenna detects the magnetic �eld part of radio wave.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 196
Magnetic Core
(Ferrite)
Loop Antennawith many turns
Loop Antennawith many turnsand Ferrite Core
Figure 8.39: Two common loop antennas.
Electric Field
BroadcastAntenna
Earth ReceivingAntenna
Vertical Polarization
Figure 8.40: Vertically polarized radio wave.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 197
Electric Field
BroadcastAntenna
ReceivingAntenna
Earth
Horizontal Polarization
Figure 8.41: Horizontally polarized radio wave.
2 Mutually Perpendicular
Antennas
Circularly Polarized Wave
Figure 8.42: Broadcasting with circular polarization.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 198
BroadcastAntenna Ground Wave
Earth
Figure 8.43: Low frequency ground wave follows curvature of earth.
BroadcastAntenna Straight Line
Path
Earth
Figure 8.44: Direct (line-of-sight) mode of propagation.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 199
Earth
300 Miles
D
F1
F2
30 Miles
70 miles
50 Miles
150 Miles
Ionosphere
Figure 8.45: Earth's ionosphere layers.
BroadcastAntenna
Reflected Sky
Wave
Ionosphere
Earth
Figure 8.46: Sky wave world communications.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 200
BroadcastAntenna
Ionosphere
Earth
Figure 8.47: Two-hop transmission of radio wave using ionosphere.
Earth
Geostationary Satellite
Figure 8.48: Communication using a satellite.
CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 201
Dial on Tuner
99.6 100
100.2
100.4
99.8
MHz
Figure 8.49: Selectivity relates to how well alternate channels are rejected.
BroadcastAntenna Receiver
Direct
Reflected
Figure 8.50: Direct and re ected waves from a broadcasting station.
Receiver
100 Mhz
100 Mhz
Should be suppressed
Figure 8.51: Capture ratio in tuner.
Chapter 9
Analog Recording and
Playback
202
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 203
Top View
Side View
LeftChannel
RightChannel
Figure 9.1: Record with grooves representing mechanically engraved waves.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 204
Output
Piezoelectric Element
MagnetS
Piezoelectric Pick-up
Moving Magnet Pick-up
N
Figure 9.2: Phono playback systems.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 205
90˚
Left
Right
Figure 9.3: Stereo with only one stylus.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 206
S N
Figure 9.4: A stereo moving magnet phono cartridge.
Unmagnetized Magnetic MaterialMagnetization is Zero
Magnetized Magnetic MaterialMagnetization is Non-Zero
Magnetic Domain
Figure 9.5: Unmagnetized and magnetized magnetic material.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 207
Current
Current in Coil
Magnetic Field in Coil
Magnetic Field
Figure 9.6: Magnetic �eld produced by a coil when current ows through it.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 208
Current in Coil
TotalMagnetization
Saturation
Figure 9.7: Alignment of domains in a magnetic material.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 209
Current in Coil
TotalMagnetization
Rententivity
Saturation
Figure 9.8: Behavior of magnetic material in a coil whose current is increasedand decreased to zero.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 210
Current in Coil
Magnetization
CoercivityCurrent in Coil
Figure 9.9: Memory is destroyed by reversed current in coil.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 211
Magnetic Field of Coil
Magnetization
Magnetic Field of Coil
Magnetization
Figure 9.10: Hysteresis curve of magnetic material.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 212
Soft
Hard
Figure 9.11: Groups of magnetic materials.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 213
1L 1
1R 2
2L 3
2R 4
Magnetic Particles
Polyester Film
Heads
Side View
Top View
Stereo
Figure 9.12: Side and top views of magnetic tape.
Figure 9.13: Magnetic particle of gamma { Iron (III) Oxide as used on tapes.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 214
AudioInput
Tape Motion
N S
S N N S
Figure 9.14: Recording head aligning magnetic domains on tape.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 215
1 Wave
Domain AlignmentS N
Domain Alignment
SN
Audio Signal:
Top Viewof Tape
1 Wave
Audio Signal:
Top Viewof Tape
Figure 9.15: Analog recording on a magnetic tape.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 216
N S NS N S NS
1 Wave 1 Wave
High Frequency Low Frequency
Figure 9.16: Recorded information on magnetic tape.
Tape Motion
Output
Gap (Exaggerated)
NS N S
Figure 9.17: Playback head for reading information on a tape.
Tape Motion
Output
1 Wave
NS N S
Figure 9.18: Playback head reading signals.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 217
Erase Record Playback
Tape
Figure 9.19: Order of heads on a tape deck.
Magnetization
Magnetization
Recording Currentin Coil
Recording Currentin Coil
Figure 9.20: Recording on material with magnetic hysteresis.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 218
Magnetization
Recording Currentin Coil
Input Currentto Coil
RecordedInformation
Figure 9.21: Recording a signal on a tape.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 219
Magnetization
Current in Input Coil
Recorded Information
InputInformation
Linear Characteristic of Tape
Figure 9.22: Ideal magnetic characteristics for tape | linear behavior.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 220
Magnetization
Currentin Coil
Region to be avoided
Almost Linear Regions
Figure 9.23: Useful region on hysteresis curve for magnetic recording.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 221
0
+
Audio + Bias on Tape
Audio + Bias Input
Audio Output
Audio InputA-C Bias Input
Figure 9.24: Recording on magnetic tape with bias.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 222
Erase Record Playback
BiasOscillator
Recording Amplifier
AudioSignal
PlaybackAmplifier
Figure 9.25: Details of heads for magnetic recording.
Frequency
Output fromPlayback Head
20,000 Hz20 Hz
Figure 9.26: Frequency dependence of output from playback head.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 223
Frequency
Output fromPlayback Head
20 kHz20 Hz 10 kHz
4 m Gap
Frequency
Output fromPlayback Head
20 kHz20 Hz 10 kHz
17/8 i.p.s.
71/2 i.p.s.
15 i.p.s.
µ
2 m Gapµ
1 m Gapµ
Figure 9.27: Output from playback head as a function of frequency forvarious gap sizes and tape speeds.
Frequency
Output(dB)
20 kHz20 Hz 10 kHz1000 Hz100 Hz
120 sec Equalizationµ
70 sec Equalizationµ
Figure 9.28: Equalization in playback.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 224
Frequency
Output(dB)
20 kHz20 Hz 5000 Hz
Figure 9.29: Equalization in recording.
Time
Amplitude
Average Sound Levels
Transients
Figure 9.30: Typical musical spectrum.
CHAPTER 9. ANALOG RECORDING AND PLAYBACK 225
Frequency
RecordingLevel(dB)
20 kHz10 Hz 10 kHz
0
-10
-20
1 kHz
Figure 9.31: Frequency response at di�erent recording levels.
X Y
Figure 9.32: Exercise 9.4.
Chapter 10
Digital Optical Recording &
Playback
226
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 227
Time
Pressure
Time
Voltage
ContinuousRepresentation
Figure 10.1: Sound wave and its analog representation as a voltage.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 228
Groove
Scratch
Very Large Amplitude Signal
High Frequency Signal
Figure 10.2: Grooves on a record representing analog signals.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 229
Playback
Tape MotionDirt
Played Back SignalRecorded Signal
Tape
Figure 10.3: Distortion of analog signal by dirt stuck between playback headand tape.
2Original Number 2 Worn out Number 2
Figure 10.4: Original number 2 and worn out number 2; basic informationis not lost when number is worn out.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 230
Amplitude(Decimal)
Time0
8
42
Amplitude(Binary)
Time000000100100
1000
Figure 10.5: (a) Analog signal, decimal scale (b) Analog signal, binary scale.
Time
20 Hz
200 HzTime
Figure 10.6: 20 Hz wave will get more samples per wave than a 200 Hz wave.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 231
Samples (not enough!)
SignalAliased Signal
Samples (good!)
Signal
No Aliasing
Figure 10.7: Aliasing due to inadequate sampling rate.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 232
Frequency
Signal
Sampling Frequency
FS F + F / 2SS
Frequency
Alias Zone
FS F + F / 2SSF > F / 2S
Poor, Aliasing, Maximum Signal Frequency F > F / 2S
Good, No Aliasing, Maximum Signal Frequency F = F / 2S
F = F / 2S
Figure 10.8: Audio spectrum and sideband frequencies due to sampling.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 233
Sampling Points
Amplitude
Time
Holds
Sample and Hold of Analog Signal
Figure 10.9: Sample and hold of a signal for digitizing.
Right
Left
MultiplexerOut
In
In
2 Channels 1 Channel
Figure 10.10: Multiplexing of left and right channels.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 234
Analog Signal Sampled Analog Signal Digital Signal
Sample&
Hold
Low-PassFilter
Left Channel
A/DConverter
Sample&
Hold
Low-PassFilter
Right Channel
A/DConverter
FirstMultiplexer
1000 011101100100 0101
00110011
0010 0010
00010001
Figure 10.11: Digitizing a signal.
Output from D/A Converter
Figure 10.12: Output of D-A converter.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 235
Output from D/A Converter
Smoothing byLow-pass
Filter
Figure 10.13: Output of low-pass �lter.
D/A Converter Low-PassFilter
Left ChannelIn
Left ChannelAnalog Out
Digital
0100100011011001
Figure 10.14: Main features of playback of digital signal.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 236
Disc Travels Slower
Disc Travels Faster
Pits and Lands
To keep constant Laser Beam to Disc Speed
Figure 10.15: Details of information on a CD.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 237
Pit 1/4 Wave
Out of Phase by 1/2 Wave
Land
Laser Beam
Figure 10.16: Interference between light beam re ected from pit and from at.
PitsLabel
Compact Disc
Protective Layer
Metal Film Layer
Transparent Substrate
Lens
In
Out
Laser Beam
Figure 10.17: Focusing action of a laser beam by lens.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 238
Compact Disc
Lens
Laser Beam
Dirt
Dirt out of Focus
Figure 10.18: Reduced e�ect of surface defect on CD.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 239
Pit Length
Land Length
Pit Land
0.8 mµLaser Beam
0.5 mµTrack Width
1.6 mµTrack Pitch
Figure 10.19: Laser spot focused on disc data.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 240
Laser Beam to Track
Laser Beamto Read
DiscDirection
Laser Beam to Track
Pit
Figure 10.20: Three-beam detection; one for read-out and two beams fortracking.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 241
Plane PolarizedRandomly Polarized
WaveWave
Figure 10.21: Randomly polarized beam and plane-polarized beam.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 242
Horizontally Polarized Light
Cylindrical LensConverging Lens
Beam Splitter
Objective Lens
Compact Disc
To Detector
1/4 Wave Plate
Vertically Polarized
Light
Out
In from Laser
CircularlyPolarized
Light
Figure 10.22: Path of laser beam and role of its polarization.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 243
Coherent Beam of Light
Incoherent Beam of Light
Figure 10.23: Coherent and incoherent beams of light.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 244
Current
Rear Mirror
Current
pn Junction
Front Mirror
Laser Beam
Figure 10.24: Semiconductor laser.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 245
4 Oversampled×
Sampled Signal
2 Oversampled×
Figure 10.25: E�ect of 2-times and 4-times oversampling.
CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 246
Mini Disc
Optical Readout
In: 1.4 MBit / Second
Out: 0.3 MBit / Second
Memory
Figure 10.26: Shock-proof memory in mini-disc.
Chapter 11
Digital Magnetic Recording
& Playback
247
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK248
Track
Magnetic Domains
Figure 11.1: Magnetic digital signals recorded vertically on a mini disc.
RecordingMagnetic Head
Mini Disc
Protective Layer
Substrate
Lens
Laser Beam
Magnetic Recording
Layer
Signal In
Figure 11.2: Recording digital signals on a mini disc.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK249
N
S
Rotation of Polarization Plane
Reflected
Laser BeamIn
Polarization
Magnet
Figure 11.3: Kerr e�ect: plane of polarization of light beam rotates uponre ection from a magnetized surface.
Lens Lens
Polarization Plane
In Out
Record Head
Record Head
Figure 11.4: Read-out of digital information using Kerr e�ect. Magnetic�eld direction a�ects plane of polarization of re ected laser beam.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK250
Change in Intensity
Lens Lens
In Out
Recordable Disc
Change in Polarization Plane
Kerr Effect
Lens Lens
In Out
Bright Less Bright
Prerecorded Disc
InterferenceEffect
Recordable Disc
Figure 11.5: Di�erence in read-out between pre-recorded and recordablemini-discs.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK251
Magneto-optic Layer
Reflective Layer
SiN
SiN
Pre-groove
Pre-grooved for Tracking
Laser Spot
Figure 11.6: Section of a recordable mini disc.
Program AreaLead-in Area
Lead-out Area
Figure 11.7: Layered structure of recordable mini disc.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK252
Lower Sector
Upper Sector
Figure 11.8: Track pattern in DCC tape.
Upper Sector
Left
Right
Record Read
DCC Head
Analog Playback
Only
012345678
012345678
Record Playback
Digital
Figure 11.9: The playback head reads only a portion of the recorded track.
.02 .05 .1 .2 .5 1 2 5 10 20 kHz
SPL-dB
Treshold of Hearing
Frequency
Figure 11.10: Threshold of hearing curve.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK253
.02 .05 .1 .2 .5 1 2 5 10 20 kHz
SPL-dB
New Treshold
Record
Ignore
Frequency
Figure 11.11: Sounds which will be recorded by PASC and masking of quietpassages.
Tape
1 1
0
Audio Signal:
Figure 11.12: Representation of digital signal on magnetic tape.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK254
Slanted Tape Path
Tape
Audio Tracks
Head Drum
Record / Play Head
Figure 11.13: Helical recording with rotating heads.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK255
90˚
Record / Play Head B
Record / Play Head A
Tape
Figure 11.14: Tape contact to rotating head.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK256
Head B
90˚Wrap Angle
Head A
One Revolution
Signal
Signal
Head A
Head B
1/4 Revolution
Figure 11.15: Time compression to reduce wrap angle.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK257
Side A
Side B
Guard Band
Left
Left
Right
Right
Analog Cassette Track Pattern
Figure 11.16: Guard band between tracks on analog tape reduces cross-talk.
Tape
Head B
Guard Band not necessary
Head A
Figure 11.17: Azimuthal recording.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK258
Tape
+ 20˚ Azimuth
- 20˚ Azimuth
B A
Figure 11.18: Digital information on magnetic tape recorded longitudinally.
CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK259
Tape
Audio
AB
Subcode ATF
SubcodeATF
Figure 11.19: Arrangement of signals on a tape.
XY
+
Figure 11.20: Exercise 11.7.
Chapter 12
Heat
260
CHAPTER 12. HEAT 261
Friction causes Heating
Mechanical Friction
Electrical "Resistance" due to Collisions of Electrons and Vibrating Ions
Moving Electrons
Vibrating Ions+
++
+
+
+
Metallic Wire
Stylus
Friction causes Heating
Groove
Motion Friction causes Heating
Friction causes Heating
Figure 12.1: Sources of heating in hi-� due to mechanical friction and elec-trical \friction".
CHAPTER 12. HEAT 262
Current
Heat
Voice Coil
Speaker
DiodeCurrent
ResistorCurrent
HeatHeat
Heat
Current
Transistor
Figure 12.2: Electrical \friction" causes heating in ampli�er componentsand voice coil.
CHAPTER 12. HEAT 263
Alcohol
0 °C
100 °C
Pressure
Gas
Figure 12.3: Two types of thermometers: alcohol expansion thermometerand gas thermometer.
CHAPTER 12. HEAT 264
-50 °CTemperature
ElectricalResistancein arbitrary
units
0 °C 50 °C 100 °C
Cold Hot
Figure 12.4: Temperature dependence of electric resistance of a semiconduc-tor.
Resistance Thermometer Element
CurrentMeter
Battery
Figure 12.5: Basic circuit for resistance thermometer.
CHAPTER 12. HEAT 265
TbFeCo
Aluminum
Laser Beam
Section of Mini-Disc Section of Mini-DiscT above CurieTemperature
T at Room Temperature
≈ 1000 Å
To Record
Figure 12.6: Heating of spot on mini-disc for recording.
Hot Cold
Heat Flow
LargeAmplitude
SmallAmplitude
Figure 12.7: Heat conduction along a bar between a hot body and a coldone.
CHAPTER 12. HEAT 266
Hot Cold
Hot Cold
Heat
Heat
Smaller Thermal
Resistance
Larger Thermal
Resistance
Figure 12.8: Thermal resistance depends on length of heat conductor.
CHAPTER 12. HEAT 267
Hot Cold
Heat
Smaller Thermal
Resistance
Larger Thermal
ResistanceHot Cold
Heat
Cross-sectional Area
Figure 12.9: Thermal resistance depends inversely on cross-sectional area ofheat conductor.
CHAPTER 12. HEAT 268
Source of Heat
Cold Air
Warm Air
Figure 12.10: Transfer of heat in air by convection.
Object Temperature = T
+ +Vibrating Charges
ElectromagneticWave
Figure 12.11: Object at temperature T emits electromagnetic waves.
CHAPTER 12. HEAT 269
Vibrationof Atoms
Vibrationof Atoms
At some Temperature
When Temperature has Increased
Figure 12.12: Thermal expansion of an object when heated.
Brass
Steel Cool
Hot
Flame Ice
Figure 12.13: Bimetallic strip and its behavior when heated or cooled.
CHAPTER 12. HEAT 270
Transistor
Unmounted Diode
Heat Sink withLarge Area
Heat Sink withLarge Area
Mounted
Figure 12.14: Mounting of transistor and diode on heat sink to transferheat away from devices by heat conduction.
CHAPTER 12. HEAT 271
Holes
Hot Air Radiation
Cold Air Holes
Convection
Figure 12.15: Heat removal by convection and radiation.
Too Hot
Open Circuit
Current In
Current Out
Reset ButtonMaterials with different
Expansion Amounts
Figure 12.16: Action of circuit-breaker when too hot.
CHAPTER 12. HEAT 272
Write Head
Spot Heated above Curie Temperature
Magnetic Film
Write Head
Spot Cools in Field of Write Head
Motion
Heat to Record Recorded
Laser Off
Signal InSignal In
Figure 12.17: Thermo-magnetic recording on mini-Disc.
Chapter 13
Mechanics
273
CHAPTER 13. MECHANICS 274
Recording Head
Direction of TravelDistance travelled in
Elapsed Time
Tape
Figure 13.1: Speed of tape past recording head.
Earth
Figure 13.2: Time for a radio wave to go around the Earth at the equator.
CHAPTER 13. MECHANICS 275
Rotation
Velocity is 0.4 m/sec, left
Velocity is 0.4 m/sec, down
Phono Record
X
Y
Figure 13.3: Speed of a recorded signal is the same at X and at Y; theirvelocities are di�erent.
CHAPTER 13. MECHANICS 276
+
+
Fixed Magnet
NSForce
Fixed Magnet
NSForce
Figure 13.4: Force on voice coil giving it a push or a pull depending ondirection of current in voice coil.
CHAPTER 13. MECHANICS 277
Capstan
Tape
Pinch-Roller
Tape Direction
Force
Figure 13.5: Force on tape by capstan-pinch roller.
Capstan
Tape
Pinch-Roller
Tape Direction
Force of Static Friction
No Motion between Tape and Pinch-Roller and Capstan
Figure 13.6: Static friction-force pulling on tape.
CHAPTER 13. MECHANICS 278
Clips
CD
Figure 13.7: Releasing a CD from its case by applying a pressure on theclips with a �nger.
CHAPTER 13. MECHANICS 279
Woofer has Large Inertia
Tweeter has Small Inertia
Figure 13.8: Inertia of a tweeter is less than that of a woofer.
CHAPTER 13. MECHANICS 280
Outer Ear
Eardrum
Sound
Figure 13.9: Outer ear; ear drum's inertia limits response at frequenciesabove 20 kHz.
Stylus
CartridgeTone Arm
Weight of Cartridge for Tracking Groove in
Phono Record
Figure 13.10: Adjusted weight in cartridge for helping the stylus to trackthe groove in phono record.
CHAPTER 13. MECHANICS 281
Information Tracks on CD
Fixed Magnet
Current(Audio)
N S
Speaker Mechanism
Focus Coil
Moving Coil to Focus
Laser Beam for CD
Lens
S SN N
Figure 13.11: Force of clampedmagnet on a voice coil accelerates diaphragmin loudspeaker. Force of clamped magnet on focus coil accelerates focus lensin CD player.
CHAPTER 13. MECHANICS 282
Wall
Pulse on String Pulls on Wall
Wall
Wall Pulls on String causing
Pulse
Figure 13.12: Re ection of a pulse on a string clamped at wall and itsinversion.
CHAPTER 13. MECHANICS 283
Bar Magnet
Current
N S
Force on Voice Coil
Force on Bar Magnet
Because of this, Magnet must be clamped
Figure 13.13: Force on voice coil and force on magnet.
CHAPTER 13. MECHANICS 284
Phono Record
Both at same Frequency
Constant Frequency of Rotation
CD
Both at same FrequencyVariable Frequency of Rotation
Figure 13.14: Waves recorded on a phono record and a CD.
CHAPTER 13. MECHANICS 285
Phono Record
Circumference at
Circumference at
router
r inner
r inner
router
2 routerπ
2 r innerπ
Figure 13.15: Distances covered along outer track and inner track on aphono record.
CHAPTER 13. MECHANICS 286
CD
Rotation Rate at 200 rpm
Rotation Rate increased to 500 rpm
Figure 13.16: Frequency of rotation of a CD is made higher near the inneredge and lower near the outer edge to maintain constant linear speed on atracks.
Record / Play Heads
Tape Guide
Tape
2000 rpm
Drum
Figure 13.17: Rotation of drum head relative to magnetic tape in DAT.
CHAPTER 13. MECHANICS 287
A. Harder to Open
CD
CD Case Lid
B. Easier to Open
CD
CD Case Lid
Figure 13.18: When same force is applied to the CD case lid, it is easier toopen the lid near the edge because torque is larger there.
CHAPTER 13. MECHANICS 288
A
DistanceLid
Hinge Point
B
Distance
Lid
Hinge Point
Force
Force
Small TorqueLarge Torque
Figure 13.19: For the same force exerted on lid, the torque is larger in Bthan in A.
CD
MD
Figure 13.20: Moment of inertia of a CD is larger than that of a mini-Disc.