High Performance Audio Power Amplifiers

by Duncan

• ISBN13: 9780750626293
• ISBN10: 0750626291
• Format: Hardcover
• Copyright: 1996-11-08
• Publisher: Elsevier Science

Summary

Power amplifiers and their performance lie at the heart of audio engineering and provide some challenging problems for the engineer. Ben Duncan's experience, as an audio consultant, analog electronics designer and author, give him an unique insight into this difficult but rewarding field. Linking analog electronics, acoustics, heat and music technology; high-end hi-fi and professional PA and recording studio use; theory, modelling and real-world practice; design and repair; the old and the new, the mainstream and the specialised, this comprehensive guide to power amps is a core reference for anyone in the industry, and any interested onlookers. Ben Duncan is well known to many users of audio power amplifiers around the world, both professional and domestic, through his articles, reviews and research papers on music technology in the UK and US press, and through his part in creating several notable professional power amplifiers. Since 1977, he has been involved in the design of over 70 innovative, high-end audio products used by recording and broadcast studios, on stages, in clubs and by the most critical domestic listeners - as well as creating bespoke equipment for top musicians. Born in London, he has travelled widely but has lived mainly in Lincolnshire, home of his family for over 150 years. He is twice co-author of the book Rock Hardware in which he has chronicled the history of rock'n'roll PA. Reprinted with corrections September 1997 Comprehensive and colourful real-life guide Based on wide experience of audio and music technology Well-known and prolific author in the hi-fi and pro-audio press

Table of Contents

Preface	xi
Acknowledgments	xiii
System of persentation	xv
Introduction and fundamentals	1	(18)
What are audio power amplifiers for?	1	(1)
What is the problem?	1	(1)
What is audio?	2	(1)
What's special about audio?	2	(1)
The ramifications of quality on audio	3	(1)
Some different aims of sound reproduction	3	(1)
About people and their hearing	4	(1)
Limits of a `objectivity'. Why listen?	5	(1)
Why are power amplifiers needed for audio?	6	(2)
Music fundamentals	8	(1)
Adjectives that describe sound	9	(1)
Tonal qualities	10	(1)
Broader tonal descriptors	11	(1)
General sonic adjectives	11	(1)
Dynamics	12	(1)
Space	13	(1)
Botheration or Abomination	14	(1)
Nature and range of music (alias programme)	14	(1)
Bass and subsonic content	15	(1)
HF dynamics and ultrasonic content	16	(3)
References and Further reading	18	(1)
Overview of Global Requirements	19	(30)
Common formats for power amps	19	(2)
Loudspeakers	21	(11)
Loudspeaker drive-unit basics	21	(4)
Loudspeaker sensitivity vs. efficiency	25	(1)
Loudspeaker enclosure types and efficiencies	26	(1)
Loudspeaker configurations: a resume	27	(5)
The interrelation of components	32	(8)
What loudspeakers look like to the amplifier	32	(3)
What speakers are looking for	35	(3)
What passive crossovers look like to amplifiers	38	(2)
Behaviour of power amps as voltage sources	40	(6)
Drive-unit power ratings after EIA/AES	40	(1)
Output power capability requirements	41	(2)
Loudspeaker vulnerabilities	43	(1)
High power, the professional rationale	44	(2)
Active systems, power delivery requirements	46	(1)
Current delivery requirements	46	(3)
The low impedance route	47	(1)
References and Further reading	48	(1)
The input port - Interfacing and processing	49	(34)
The Input	49	(9)
Input sensitivity and gain requirements	49	(3)
Input impedance (Zin)	52	(6)
RF filtration	58	(1)
The balanced input	59	(4)
Balancing requirements	59	(1)
Introducing Common Mode Rejection	60	(3)
Sub-sonic protection and high-pass filtering	63	(5)
Direct Coupling	65	(3)
Damage protection	68	(3)
What are process functions?	71	(9)
Common gain control (panel attenuator)	71	(3)
Remotable gain controls (machine control)	74	(3)
Remote control considerations	77	(1)
Compression and limiting	78	(1)
Clipping (overload) considerations	79	(1)
Clip prevention	79	(1)
Soft-Clip	79	(1)
Computer control	80	(3)
References and Further reading	82	(1)
Topologies, classes and modes	83	(86)
Introduction	83	(4)
About topologies	84	(3)
Germanium and early junctions	87	(8)
Out of the vacuum-state	87	(1)
Push-pull, Transformer-coupled	88	(1)
Sub-topology: the Darlington	89	(2)
Transformerless push-pull (transistor OTL)	91	(1)
Sub-topology: diode biasing	91	(1)
Complementary push-pull OTL	92	(2)
Quasi complementarity: the faked match	94	(1)
Sub-topology: paralleling	94	(1)
Silicon transistors	95	(10)
The Lin topology	96	(2)
Sub-topology: the long-tailed pair (LTP)	98	(1)
Sub-topology: the Vbe multiplier (VbeX]	99	(1)
Sub-topology: the triple (compound BJT)	100	(2)
Sub-toplogy: Dual supplies (+/-Vs)	102	(2)
Sons of Lin	104	(1)
True Symmetry: the sequel	105	(8)
Later topologies	106	(2)
IC power	108	(2)
The Op-Amp topologies	110	(2)
Power cascades and cascodes	112	(1)
Introducing bridging	113	(5)
Bridging the bridge	117	(1)
Class-ification	118	(18)
Class A	118	(5)
Class A alternatives	123	(1)
Class A sliding bias and `II-mode'	123	(3)
`Super Class A'	126	(1)
Dynamic biasing and Stasis	126	(1)
Sustained plateau biasing	126	(1)
Class B and A-B	127	(4)
Class A-B, developments and ameliorations	131	(5)
Introducing higher classes	136	(10)
Class G	138	(3)
Class H	141	(2)
G and H, the comparison	143	(3)
Beyond analogue	146	(7)
Class D	147	(5)
`Digital' amplification	152	(1)
Class summary	153	(2)
Introducing modes of control	155	(9)
Negative feedback modes	156	(6)
Other Error Correction Modes	162	(2)
Conclusions	164	(5)
References and Further reading	168	(1)
Features of the power stage	169	(62)
Overview	169	(2)
Operating with high voltages	169	(1)
Operating with high currents	170	(1)
Power devices	171	(13)
Bipolar Junction Transistors (BJT)	171	(6)
Mosfets (enhancement-mode power FETs)	177	(6)
Insulated Gate Bipolar Transistors (IGBT)	183	(1)
Recognising large signals	184	(7)
The slew limit	185	(6)
RF stability	191	(2)
Power stage, critical layout requirements	191	(1)
Critical nodes	192	(1)
V&I limits on output, the context	193	(20)
V-I output capability	198	(2)
V-I output limiting (adverse load protection)	200	(10)
Mapping V-I capability	210	(1)
Audio protection, by fuse	211	(2)
Clip indication - external relations	213	(5)
Overdrive behaviour - internal relations	215	(1)
Output stability and the output network (OPN)	215	(2)
RF protection	217	(1)
DC offset, at output	218	(2)
DC (Fault) protection (DCP, DCFP)	219	(1)
The output interface	220	(2)
Muting systems	221	(1)
Output stage, cooling requirements	222	(6)
Heat exchange	224	(2)
Thermal protection	226	(2)
Logical systems	228	(1)
Output transformers	228	(3)
References and Further reading	230	(1)
The power supply	231	(26)
Mains frequency (50/60Hz) supplies	231	(9)
50/60Hz EMI considerations	235	(2)
Surge handling	237	(1)
Actively-adaptive 50/60Hz PSU	238	(1)
Regulated 50/60Hz `passive' supplies	239	(1)
Supply amongst channels	240	(3)
Bridge benefits	242	(1)
Operation with 3 Phase AC	242	(1)
Pulse-width power (PWM PSU)	243	(8)
HF power supplies (SMPS, HF switchers)	244	(3)
Resonant power	247	(3)
The higher adaptive PSUs	250	(1)
HF switching summary	250	(1)
Power supply (PSU) efficiency round-up	251	(2)
Amplifier efficiency summary	252	(1)
Power supply fusing	253	(4)
References and Further reading	256	(1)
Specifications and testing	257	(58)
Why specifications?	257	(2)
Types of spec	257	(2)
Standards for audio power amps	259	(1)
Why test things?	259	(6)
Test tools and orientation	260	(1)
Realtime test signals	261	(3)
The test equipment revolution	264	(1)
Physical environment	265	(7)
Mains measurement and conditioning	265	(1)
Power amplifier preconditioning	266	(2)
The test load	268	(4)
Frequency response (Bandwidth, BW)	272	(9)
Gain and balance	274	(2)
Output impedance (Zo)	276	(2)
Damping factor	278	(1)
Phase response	278	(3)
Introducing noise	281	(5)
Noise spectra	282	(1)
Breakthrough and crosstalk (channel separation)	283	(1)
Understanding CMR measurements	284	(1)
Measuring CMR	285	(1)
Input impedance (Zin)	286	(1)
Introducing harmonic distortion	286	(18)
Harmonics: the musical context	289	(4)
Harmonic distortion (THD, %THD+N)	293	(4)
Individual harmonic analysis (IHA)	297	(1)
Intermodulation (% IMD, Intermod)	298	(4)
Dynamic intermodulation (% DIM 30/100)	302	(1)
Sundry intermodulation checks	303	(1)
Other distortion tests	303	(1)
Power output (Po)	304	(4)
Output voltage capability (Vo rms, MOL)	305	(1)
Dynamic output capability	306	(1)
Clipping symmetry	307	(1)
Dynamic range	308	(1)
Dynamic tests	308	(7)
Rise time (small signal attack)	308	(1)
Slew limit (slew rate, large signal attack)	309	(1)
Transient response (impulse response)	310	(2)
Peak output current capability	312	(2)
References and Further reading	314	(1)
Real world testing - rationale and procedures	315	(16)
Scope and why essential	315	(1)
Listening	315	(2)
Operable mains range	317	(4)
Inrush current	318	(1)
Soft start	319	(1)
Mains current draw	320	(1)
Signal present indication and metering	321	(1)
Clip indication	322	(1)
DC at the input	322	(1)
RF at input	322	(1)
Large signals at input	323	(1)
Output DC offset (output offset, Voos)	323	(4)
RF at output	324	(1)
Adverse loads	325	(1)
Adverse load proving	325	(1)
Adverse loads, low loads and shorting	325	(2)
Adverse loads, reactive	327	(1)
Hard drive testing	327	(1)
Thermal protection and monitoring	327	(1)
Muting behaviour	328	(1)
Acoustic noise	328	(1)
EMI and EMC	329	(2)
References and Further reading	330	(1)
Choice, application installation and set-up	331	(46)
Manufactured goods, a resume	331	(9)
Choosing the right power amp, domestic	332	(3)
Choosing the right power amp, for pro users	335	(5)
Howlers	340	(2)
AC mains voltage	342	(14)
Safety earthing	344	(2)
Mains cabling	346	(2)
Power factor correction	348	(1)
Mains fuses and breakers	349	(1)
AC mains connectors, amplifier end	350	(2)
AC mains connectors, the power-end	352	(1)
Mains wiring practice, domestic and studio	352	(4)
Input connections	356	(6)
Balanced polarity and shielding	359	(1)
Quasi balanced (unbal-to-bal)	360	(1)
Input cabling	361	(1)
Output connections	362	(9)
Speaker cabling	367	(3)
Impedance setting	370	(1)
Output polarity	370	(1)
Placement and fitment	371	(3)
Cooling airflow conventions	371	(2)
Cooling and air pollution	373	(1)
The 1 to 5 of prudent amplifier use	374	(3)
System back-end troubleshooting	374	(2)
References and Further reading	376	(1)
Maintenance and surgery	377	(80)
Classifying failures	377	(2)
Problem solving procedures	379	(1)
Universal repair procedures	379	(10)
Repair tools and equipment	389	(4)
Useful tools	389	(1)
Test powering tools	390	(2)
Audio test tools	392	(1)
Testing components	393	(5)
Testing BJTs (bipolar transistors)	393	(2)
Testing Mosfets	395	(2)
Testing diodes, zeners and LEDs	397	(1)
Scope traces	398	(3)
References and Further reading	400	(1)
Useful addresses for maintenance	400	(1)
Appendices
1 History	401	(8)
2 Makers' listings	409	(6)
A-Z, under principal use	409	(4)
A-Z of integrated loudspeaker-amplifier makers	413	(1)
Principal output device, by number of makers	414	(1)
3 Active devices	415	(8)
A Bipolar transistors, silicon	416	(4)
B Lateral power Mosfets	420	(1)
C Power D-Mosfets	421	(1)
D Thermionic valves (electron tubes)	422	(1)
4 Power amplifier terminology	423	(34)
Index	457