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Page Last Updated - May 2014


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    Active Filters Using Gyrators.
Amplifier Classes - Class-A, Class-B, etc.
Inverters - What are the differences between the different types?
Active Filters (Update)


Feature Articles Updated

Lamps + EnergyLamps & Energy - All material under this heading now has a new home with a separate index
Dec 2011
BiampBenefits of Bi-Amplification - Not quite magic, but close (Part I)May 2005
Biamp 2Benefits of Bi-Amplification - Crossovers, tri-amping, etc. (Part II)May 2005
FakeCounterfeit (Fake!) Semiconductors - Don't you be caught with fake, below spec transistors when you build a project!Feb 2011
SchoolEducation - Customised projects for schools, technical colleges and universitiesApr 2003
ManufactureThe State of Manufacturing - This article should be a mandatory read for all businessmen and politicians, a real wake-up call !May 2010
PA SystemsPublic Address Systems for Music Applications - Something of an exposé on the pitfalls of PA systems   Oct 2009
Cinema SoundCinema Sound ... Why Isn't It Excellent? - The cinema X-Curve (ISO Bulletin 2969) is used everywhere, but is it right?Mar 2012

Amplification

Amp SoundAmplifier Sound - What causes the perceived differences between amps?  Is it real or imaginary?Apr 2000
Amp ClassesAmplifier Classes - What is the difference between Class-A, Class-B and all the others? The characteristics of each are discussed   May 2014
Class AClass- A - a discussion of the benefits of Class-A amplifiersApr 2005
Class GClass- G - One of the lesser known amp classes. An explanation of how they workJan 2009
PWMClass-D (PWM) Amplifiers - Theory and design concepts behind these 'new' amplifiersJun 2005
ClippingClipping Behaviour - One of the lesser known effects of amplifier clipping, and the damage it can do.Oct 2004
70/100V Line AmpsCommercial Sound - 70V & 100V 'constant voltage' line public address systems. Learn the pitfalls before you get caught.Jun 2012
FeedbackDistortion & Negative Feedback - A detailed look at the way negative feedback reduces distortionOct 2006
Guitar AmpsGuitar Amplifiers - Often there is little point repairing, and a replacement power amp should be considered. Here is why.Feb 2011
IntermodulationIntermodulation Distortion - Interesting finding, symmetrical Vs. asymmetrical. Where did the difference frequency go?Sep 2012
GuitarMusical Instrument Amplifiers - Guitar, Bass and Keyboard Feb 2001
ReverbReverberation - The care and feeding of spring reverb tanks    Sep 2009
ProtectionShort Circuit Protection - Testing amplifiers to the limits ‡Aug 2000
Soft ClipSoft Clipping - Is adding a soft-clip circuit worth the effort?Apr 2006
SpeedThe Need For Speed - Very high speed opamps from Texas InstrumentsAug 2001
PhasePhase Angle Vs. Transistor Dissipation - A simplified approach to understanding Safe Operating AreaMar 2005
SIMSound Impairment Monitor - Is This The Answer? - A new method to monitor distortion in real timeSep 2000
SOATransistor Safe Operating Area - What is SOA, and how does it affect amplifier designsAug 2003
ValveValves & Amplifiers - A new section that includes information about valves, myths, etc.Jan 2010

Cables

CableThe Truth About Cables, Interconnects and Audio in General - A 'must read' article Sep 2002
White PaperMore Truth About Cables - A white paper discussing speaker cables and interconnects *‡ Jul 2001
Cable ZCable Impedance - Characteristic impedance, high capacitance designs and amp stability Oct 2003

General Information

A-weightingA-Weighting And Sound Measurements ... How the indiscriminate use of A-weighting causes grief  Sep 2012
A-BA-B Switch Box for Amplifier Comparisons - Something to offend everyone, or a great tool? ‡Aug 2000
ABXABX Comparator - A true ABX system that does not need a PC or microcontroller ‡Aug 2002
AMAM Radio - Approaches to high fidelity AM broadcast band reception ‡Feb 2006
PartsBuying Parts - A general look at the parts you need for electronics hobby work.Oct 2007
CapsCapacitors - What are the influences that determine the so-called 'sound' of capacitors. Covers dielectrics, dissipation factor, etc.Oct 2005
CD etcCD, SACD and DVD-A - A Comparison of the formats in a discussion between Niklas Ladberg and Ing. Ohman (very interesting) ‡Aug 2002
CompressionCompression In Audio - Ever wondered why some music sounds flat and lifeless, even though it's loud?Dec 2001
DC and TransformersDC Offset and Transformers - Many people have found that toroidal transformers growl at times. This explains why, & how to fix it.Mar 2008
Compound vs. DarlingtonCompound vs. Darlington - An explanation of the differences between Compound (Sziklai) and Darlington pairs.Jan 2011
EarthingEarthing Your Hi-Fi - Tricks and Techniques - How to eliminate hum without affecting safetyDec 1999
ElectrocutionElectrocution - How to avoid being electrocuted, what to do if the worst happensApr 2007
FusingFusing - Circuit protection, how to select the right circuit protection device to prevent serious damage ‡   Sep 2009
HeatsinkHeatsink - Build Your Own? - Yes, it can be done. If you have the tools, you can make a heatsink as big as you'll ever want.Feb 2006
50-60HzImporting Equipment From Overseas ... Effects of Voltage & Frequency on Electronic Equipment (50/60Hz can make a big difference !)   Feb 2010
IllusionIs Sound an Illusion - An interesting discussion about our perception of sound ‡   Sep 2009
ImpedanceImpedance - What does it really mean?  A general discussion on impedance, damping, etc.Jan 2005
MicsMicrophones - An introduction to the different types, polar response and behaviour of microphonesJan 2006
MythsMyths in Audio - A Look at some of the more entrenched myths, as well as some that are just too silly for words.Jul 2012
PatentsPatents - A look at the patent system, and how (or if) it affects the DIY fraternity.   ‡May 2010
Phono CartridgePhono Cartridge Loading - A detailed examination of the phono cartridge, and how loading affects responseJan 2012
Transformers - the VariacTransformers ... The Variac - One of the most useful but misunderstood pieces of workshop equipment.Feb 2009
TweetersWhy Do Tweeters Blow? - The real reason that tweeters (and other drivers) are destroyed by distortionJun 2012
What Is-1What is Hi-Fi - A contributed article on some of the subtle aspects of Hi-Fi ‡May 2001
What Is-2What is Hi-Fi (Part II) - Continuation of 'What is Hi-Fi' explaining the idea of accuracy (amongst other things)Mar 2004

Beginners' Luck - The beginners' Guide to ...

LenardElectronics Basics - The Lenard Audio site has an education section that is highly recommended for those just starting out
Beginner 1Electronics - Part 1   If you are just starting out, read these two articles first.   Covers passive components - resistors, capacitors and inductors Mar 2001
Beginner 2Electronics - Part 2  The resistor 'E' series (e.g. E12, E24, etc), Zener Diodes
Mar 2004
BasicsAmplifier Basics - How Amps Work - How amplifiers do what they doApr 2005
EfficiencyAmplifier Efficiency - Power Loss, DC voltages and current explained Jan 2000
RepairAmplifier Troubleshooting and Repair Guide  If it's broken, you may be able to fix it. This article is designed for those new to repairsApr 2003
Repair 2Amp Troubleshooting and Repair Guide - Part 2  Preamps, crossovers and other opamp circuits can cause grief tooJan 2007
BridgingBridging - How the 'Trimode' bridging system works in car power amplifiersOct 2002
EtiquetteBulletin Boards - A guide to etiquette when posting at your favourite forum ‡ GrinApr 2001
Opamps 1Designing With Opamps I - What they are, what they do, and how they do itMay 2000
Opamps 2Designing With Opamps II - Audio applications, filters, crossovers, etc.May 2000
Opamps 3Designing With Opamps III - More Filters, Specifications, Comparators, etc.May 2006
dBFrequency, Amplitude and dB - An explanation of the terms, what they mean, and how they are appliedDec 2006
MetersMeters, Multipliers & Shunts - How to use analogue and digital panel metersMay 2006
MixingMixing - Active Vs. Passive - The basic principles of mixing two or more signals, as used in simple applications through to multi-channel mixers.Oct 2010
PotsPotentiometers - what they are and how to use them in practical circuits.Jan 2003
PowerPower - An explanation of the derivation of PMPO in amplifiers.  Light reading, really GrinJun 2000
ToolsTools - The basics of the mechanical aspects of your hobby ‡Mar 2001
DividersVoltage Dividers & Attenuators - A short article describing how to design these essential circuitsDec 2002

Design Guidelines

Active FiltersActive Filters - Active filter design guide ... topologies, component selection, slope (dB/octave), transient response, etc.Jan 2014
State-Variable FiltersActive Filters, State-Variable - The state-variable active filter is one of the most versatile designs known. Find out what they can do.Dec 2012
Gyrator Avtive FiltersActive Filters Using Gyrators - Some of the simplest and most complex filters used are based on gyrators. The range is huge, but good results can be obtained with simple designs.May 2014
DesignAmplifier Design - ESP's contribution to the everlasting debateJun 2001
HEXFETsAmplifier Design With HEXFETs - Getting good performance from vertical MOSFETs is possible (Updated)Mar 2014
BalancedBalanced Driver with Floating Output - An in depth discussion of the design process ‡Apr 2002
Balanced 2Balanced Interfaces - >Essential reading for anyone designing equipment using balanced interconnects ‡ Jan 2010
CurrentCurrent Sources, Sinks & Mirrors - A discussion on these much misunderstood circuits.Apr 2007
HeatsinkHeatsinks - An article on heatsink selection, transistor mounting and thermal transfer principlesSep 2003
MOSFET RelayMOSFET Relays - Very different, but extremely useful for high power amps that will destroy any normal relayJun 2012
NoiseNoise in Audio Amplifiers - An explanation of noise figures, and how circuit noise is calculatedJan 2000
Pre-OpampOpamp Alternatives - A sample of the circuits that were in common use before opamps 'took over'Apr 2014
SupplyPower Supply Design - How to design linear power supplies - transformers, rectifiers and filtersDec 2007
SupplySinewave Generators - An examination of different sinewave generation techniques.Apr 2010
MatchingTransistor Matching Tests - Matching Bipolar or MOSFET transistors for critical amplifier applicationsDec 2001
VariableVariable Impedance Amplifiers - How you can control the output impedance of a power ampApr 2000
VCAsVoltage controlled Amplifiers/ Attenuators - An investigation into VCA techniques, including JFETs, LED/LDR modules and 'true' VCAsDec 2012

Power Supplies

SupplyBucking Transformers - Here is a bit more info than you'll find elsewhere - how to do it properlyMay 2010
InrushInrush Current - What it is, what it can do, and how to prevent it from causing problemsOct 2010
InvertersInverters - Squarewave, modified squarewave, modified sinewave, pure sinewave - What are the differences, and should you really care?Mar 2014
SupplyPower Supply Wiring - There are a lot of considerations for the wiring of a PSU - read about it hereJun 2003
RegulatorsVoltage & Current Regulators - The basics of both voltage and current regulators, and how (and where) to use themJul 2013
Transformer 1Transformers, Part 1 - The basics of transformers, what they do, and how they do it.May 2001
Transformer 2Transformers, Part 2 - The details of magnetic circuits, windings, core types and losses. Now includes current transformersOct 2012
Transformer 3Transformers, Part 3 - Designing and analysing transformers - not at all for the faint-hearted, but all very useful informationJan 2006
Transformer 3Small Power Supplies - Design of small PSUs - includes information that might save your life !May 2008

Crossovers, Filters and Signal Processing

Active Vs. PassiveActive Vs. Passive Crossovers - An explanation for the profound audible differencesJan 2004
BaffleBaffle Step Compensation - What it is and why we need to compensate for itDec 2001
DerivedDerived (Subtractive) Crossovers - An examination of these networks, and why they are unsuitable for serious useSep 2005
DSPDigital Signal Processing (DSP) - What DSPs can (and cannot) do for your systemDec 2006
NTMNTM™ Crossovers - This is a topic that has virtually zero technical information on the Net ... until now.Sep 2005
PassivePassive Crossovers - The Design of High Quality Passive Crossover NetworksNov 2001
PhasePhase Correction - Myth or Magic? - Do all-pass filters really work to correct loudspeaker phase anomalies?May 2007
SerialSerial vs. Parallel Crossover Networks - Are there any real differences?Aug 2003

Loudspeaker Design

ComplianceCompliance Scaling - Fitting just about any driver to just about any alignmentJun 2005
DopplerDoppler Distortion in Loudspeakers - Is the effect real or imaginary when applied to loudspeakers?  The results may surprise youAug 2004
ImpedanceImpedance - Effects Of Source Impedance on Loudspeaker DriversJul 2001
TransformThe Linkwitz Transform Circuit - What it is, what it does and how it does it ‡Sep 2002
Loudspeaker FailuresLoudspeaker Failure Modes - Why do loudspeakers fail? What can be done to prevent failures? Not what you expect! ‡Jun 2012
Pwr vs. EffLoudspeaker Power vs. Efficiency - There's more to this than meets the eyeDec 2006
Speakers 1Loudspeakers (Part I) - see the production of my latest triamped speaker boxes unfoldJul 2001
Speakers 2Loudspeakers (Part II) - The electronics that drive the 3-way system are describedNov 2001
PhasePhase, Time and Distortion in Loudspeakers - Is 'Time Alignment' worth the effort?Jul 2002
PikkuPikku 9 - Simple Network Lowers f3 - A useful approach for obtaining better bass from a very small loudspeaker ‡Jul 2006
Subs 1Satellites & Subwoofers - Description of the little known QB5 loudspeaker alignment.  Maximum SPL from 2-way bookshelf speakers. ‡Aug 2004
SSLSmall Satellite Loudspeaker - Using techniques described in various articles, this project should have wide appeal for home theatre ‡May 2007
Subs 2Subwoofer Conundrum - Some tips and hints on subwoofer selection, efficiency and placementMar 2004
TSPThiele Small Parameters - Determining the Thiele/Small parameters for a loudspeaker driverJan 2006
Box StuffingVolume Filling a Reflex Box - It is generally thought that vented boxes should not be filled, but this isn't necessarily the case ‡Feb 2007
WaveguidesPractical DIY Waveguides - Waveguide definition, calculation and construction ‡Dec 2006

Explanation of Symbols ...

NewThe article is new - that must come as a surprise GRIN  Less than 2 months old (typically).
REDDates in the update column indicate a new or updated (within 2 months) article. Usually accompanied by Update
GrinIndicates an article that may include humour - caution is advised
Contributed article (see copyright notice on article page)

Main IndexMain Index
Please refer to Copyright information in the individual articles. All articles are Copyright © 1998 ... 2014 Rod Elliott, unless otherwise stated.
Although it goes without saying (but I will say it anyway :-) the contributed articles and projects from all over the world have added considerably to the overall value and range of topics covered in these pages, and on behalf of all the readers of The Audio Pages, I thank you for you efforts. Writing a clear and descriptive technical article is not an easy task, but your perseverance is acknowledged, and I am grateful that you have taken the time to share your knowledge.

May the flow of input continue - for anyone who would like to contribute, please do not hesitate to contact me.


Upcoming Articles

At any given time, there are usually articles in production either by myself or contributors. It is no longer possible (or sensible) to leave hints as to what may or may not be coming, since it is so easy to get sidetracked by something new that comes along. Feel free to offer suggestions, or offer your own contribution.

Total Visitors since Jan 2001 - 

Last significant page update, Feb 2006 - rearranged each section into alphabetical order, added DIY heatsinks./ Jan 09 - added Glass-G./ Aug 09 - added active filter article./ 06 Jan 11 - Compound vs Darlington./ Jun 12 - Speaker failure + MOSFET relays./ Dec 12 - State-variable filters + VCAs./ March 2014 - added 'Inverters'.