This is a bunch of miscellaneous links to audio sites and circuits all over the world. Inclusion of a link does not mean that I agree with the idea (some of them are rubbish!), nor do I have any affiliation with the site. I have not been able to maintain constant contact (to ensure that the link is still alive), but most should be Ok - if not, please let me know.

I have no detailed information on any of the circuits, other than what is available from the original site, so please don't expect me to answer questions. If you have problems with a circuit on any of these sites, contact the site owner - not me.

Do they work? I cannot vouch for any of them - some look good, while others are a re-hash of old (sometimes outmoded) ideas. They are presented for their informational content only.

ESP's Links Policy
I may from time to time use links obtained from other sites (unless they request that this not be done), and therefore cannot (and will not) try to stop anyone else from doing the same with mine - in fact I encourage this, and only ask that my home page is included along with the links. I will always try do the same, so that everyone ultimately benefits. If you happen to recognise links that look like yours and there is no acknowledgment, then I slipped up - PLEASE let me know, and I will correct the oversight or remove the offending section if you prefer.

Please see the acknowledgment(s) at the end of this page.

• 22 Watt Audio Amplifier - simple stereo amplifier based on TDA1554
• 8 Watt Audio Amp - based on LM383
• Audio Amplifier - single chip 2W amplifier that runs on 5 Vdc to 15 Vdc, based on TBA 820M
• Hiraga Le Classe A -20W
• Lidström Improved ZEN i - class A FET amplifier (dubious - see my comments on another Zen amp, below)
• New Audio Amplifiers with Current Amplifier Outputs - basic 10W design, other designs up to 75W (Note: don't take this too seriously - it is a basic concept redrawn to look "new".)
• The 2-Channel Power Amplifier: Design and Testing - 4W amplifier based on NTE 1606

• 50 Watt Amplifier - easy to build general purpose 50 watt amp
• Cheapo amps - various - amplifier circuits using power ICs, from a few watts to 200W
• MOSFET Amplifier 230W / 400W
• New Audio Amplifiers with Current Amplifier Outputs - basic 10W design, other designs up to 75W (Actually not really new - the same basic circuit redrawn, with one interesting addition and a lot of junk! - don't take this too seriously - it is a basic concept redrawn to look "new".)
• Pass Laboratories DIY Projects - many amplifier projects
• Professional Sound Systems - for circuit diagrams of some of their PA amplifiers - technical pages, power ratings from 2x80W to 2x400W
• SDS Labs Schematics - solid state class A amplifiers
• The Leach Amp - 120W power amplifier, latest update of the "Low TIM Amplifier", claimed to be a very good sounding design
• The Leach SuperAmp - 270 watt Double Barrelled Amplifier published in Audio magazine
• The LM12 Amp - 80W amplifier based on LM12 IC
• Zen Amp and Preamp - Highly dubious design, but interesting and quite popular

• 5 Channel Current FB Car Amps - 200W current feedback amplifier design
• 20 Watt Power Amplifier

• Loudspeaker Protection circuit - DC protection circuit
• Power Follower with Dynamic Current Source (by Reinhard Haffmann) - less wasted power than true class A but not as good sound (I really don't like this circuit - uses a switching MOSFET - yecchhh !)

• AVA Versa-Kit Headphone Amplifier Do-it yourself Project
• HeadBanger Headphone Amp Construction Kit
• SDS Labs Headphone Amp - solid state amplifier
• Stereo Headphone Box - takes input from one audio power amplifier and drives many headphones with adjustable audio level, available as a kitfrom Sescom

• Cool Audio - Harris application note on PWM amplifiers
• LM12 - very compact IC for making good quality 80W audio amplifier, this IC has been used in some high quality active loudspeakers

• Audio Preamp - simple preamp for electric guitar or microphone
• Phono Preamp - tube design
• The ampage schematic collection - guitar and bass preamplifiers
• Digital Volume Control
• VOLC - this tar file consists of the schematic for a digital audio control
• Voltage controlled amplifier - three different circuits
• Voltage Controlled Audio Panner - variable gain amplifier circuit
• Voltage-controlled stereo signal attenuator

• 25L6 Amp - design without a power transformer
• Ampage - Valve (vacuum tube) amps and music electronics
• Dynaco Mark 3
• Dynaco stereo 70
• Homebrew Tube Amp Corner - FAQ's and circuits
• Klassiskt 300B slutsteg
• Klaus Schiffer's audio web site - Valve (vacuum tube) amplifiers and valve information
• KTA/KSA High End Tube Audio - many valve amplifier projects
• Musical Instrument Tube Amp Building, Maintaining and Modifying FAQ
• Pre-amplifier Project - valve preamplifiers
• SDS Labs Schematics - solid state class A amplifiers, headphone amplifier, valve amps
• Sheldon's Audio Designs - audio DACs and valve amplifiers
• Soft start for power tubes
• Tube Microphone Preamplifiers V72 (Telefunken/Siemens/Maihak/TAB) - information about the amplifier and the schematic
• Vacuum Tube Amplifier Construction Articles at the engineering musician web magazine - articles targeted at preamplifier design and construction
• Quad 22
• Zero Feedback Stereo Pre-Amplifier with Balanced & Unbalanced Inputs and Outputs

• 4 Channels Stereo Mixer
• Audio mixer for Ramsey FM10 transmitter: schematic and description, schematic also in Postscript
• Circuit Central Library - include 4 channel mixer circuit
• Dual Booster - two op-amp drives switchable to one output
• Simple 4-input mixer
• Simple audio mixer for two signal sources
• Simple audio mixer design ideas
• Transistorised Audio Mixer

• Additional RFI Protection for Line Input Circuits - 8KB PDF
• Instrumentation or true balanced input differential amplifier
• Jensen Transformers Application Notes and Schematics - many circuit examples with transformers
• Making Differential Probes - for sensing audio signal voltages across devices which are not ground referenced
• Simple differential amplifier - opamp balanced input circuit with unity gain and common mode rejection adjust

• Non-inverting amplifier - opamp circuit which provides 15 dB gain and option for balanced output
• Simple 0 to 24 dB Gain Amplifier and Balanced Line Driver - 18KB PDF

• Balanced Line Technology - information and example circuits for both input and output
• Circuit Central Library - balanced input and output circuits
• Quad Buffer - gives 4 Isolated Outputs
• Zero Feedback Stereo Pre-Amplifier with Balanced & Unbalanced Inputs and Outputs - valve circuit

Direct-Injection (DI) circuits for interfacing electronic musical instruments and amps to mixing desks.

• 10 to one voltage divider for direct input - very simple DI-box idea for your guitar amp output
• Black Box Circuit - a 40dB pad for running speaker output to DI-box, 100 Watts in / 275 mV out
• Jensen Direct Box Transformer - data sheets with example circuit diagrams
• PO-26 Passive Direct Box - circuit diagram of SescomPO-26 kit
• PO-25 Kit 1 x 3 Mic Splitter - circuit diagram of SescomPO-25 kit

• A Vacuum Tube Microphone Preamp / Direct Box Project - from January 1997 EQ Column, includes phantom power supply
• Balanced mic/line amp with TUBES - uses two 12AU7 tubes in a class-A cathode-driven input stage, followed by a class-AB1 cathode follower output stage, 6db gain, requires 90VDC and 12VDC
• Condenser microphone hookup
• IC mic preamp uses Jensen Twin-Servo topology
• Jensen Transformers Application Notes and Schematics - many microphone preamplifier related circuits
• JT-13K6-C in Simple One IC Stage Mic Preamp - 15KB PDF
• Simple microphone preamplifier - simple one transistor circuit
• Standard Microphone Preamplifier Input Circuitry - pdf file

• Electret microphone connection - how to connect electret microphones
• Electret microphone powering circuits
• Interfacing Microphones to Computer Sound Cards
• Making a rugged, connectorised microphone from a Panasonic microphone capsule
• PZM Modifications - phantom powering electret microphone capsules
• Schematics of old tube mics
• The Electret Condenser Microphone - simple basic connection diagrams

• 24db/octave Linkwitz-Riley
• 3-way 4th Order Active Crossovers for Car Audio

• 10 band audio equaliser - ascii drawing of simple circuit
• High-Q, 60-Hertz Notch Filter - very high-Q and narrow notchband
• Active Filters - Butterworth, Bessel and Linkwitz filter example circuits and equations
• Audio Graphic Equaliser - simple 7 band equaliser
• Basic gyrator design - basic building block of graphic EQ
• Five band EQ
• High-Q 60-Hertz Notch Filter - pdf file
• LMC835 - Digital Controlled Graphic Equaliser IC, take also look at application note

• Compressor using photoresistor - very basic circuit based on LED, LDR and OPAMP
• Dynacomp compressor
• Opto limiter - check also redrawn schematic
• Q&D Compressor - A complete guitar compressor/limiter design based on SSM2165, check also HTTP://members.aol.com/jorman/schem.html for info where to get the component
• Stereo Broadcast Limiter Circuit for the Ramsey FM10a/FM25 transmitter - also available in Postscript format
• Tape saturator - Schematic of analog tape compression circuit, read also circuit description

• Distortion Effect (for guitars) - three distortion circuit ideas
• Distortion effect for guitars
• Guitar Effects Boxes - guitar effect schematics and articles
• Guitar-related Circuits - effect circuit collection
• Harmony Central - contains effect information, schematics and construction tips
• LXH2 "Marshall" simulating preamp circuit - read also the description
• LXH2 Web Page - guitar amplifier and cabinet simulator circuits
• Phase Shifter - The classic, swishy sound of the 70s and 80s is coming back, provides a 0 to 180 degrees of phase shift, with a variable sweep control, for keyboards and guitar
• PracticeMan(TM) - battery powered small guitar amplifier with distortion and tone controls
• Stage Centre Reverb Unit - simple spring reverb unit
• Stellan's schematic - guitar effects. synthetisers, filters
• The Guitar Effects Oriented Web Page - FAQ's and circuit diagrams
• The LXH2 Web Page - guitar box simulator information

• CD Buddy - Karioke device
• How to filter out voice in music - very simple method

• Burwen audio processor documentation - dynamic noise filter and eliminator circuit diagrams
• Digital Potentiometers Overview - information about digitally-controlled solid-state electronic potentiometers from Dallas Semiconductor
• lxh2 spatialisation circuit
• Mixed feedback drive circuits for audio output transformers - technical paper from Lundahl Transformers in pdf format
• Noise generator - generates white and pink noise, from Synth Fool
• Square wave to sine wave converter circuit
• SSM ICs data sheets - voltage controlled amplifiers etc.
• True bypass DPDT switching - produce true bypass when effect is switched off

• CD-ROM to MD - get toslink signal from your CD-ROM drive
• Cheap TOSLINK Transmitter
• Coax Digital Out to MD - Convert the coax signals to TTL signals for Toslink module
• Optical output for Creative Infra CD-ROM - little circuit to connect your MD or DAT to your CD-ROM drive with standard optical S/PDIF cable, based on TOTX173
• SPDIF Circuits - input and output interfacing circuits
• S/P-DIF I/O Using the Epoch SoundPro HT-1869V+ Card - circuits for S/PDIF to TTL interface and TTL to S/PDIF coax

• A SCMS killer circuit - should work with all DAT decks that have a Sony CXD2601 signal processor, published in September 1992 in "Stereoplay" (ftp://ftp.cs.ruu.nl/pub/MIDI/DOC/pbscms.html)
• Copybit deleter - sets the copybit in digital audio signals to enable copying of digital recordings

• Audio Crafters Guild Articles & Essays - DAC building articles
• DAC v1.1 - high-performance DAC using the Crystal Semiconductor 8412 receiver, 8x oversampling, Burr-Brown PCM1702 D/A chips and the POOGE-5 output stage
• Jitter-Free DAC
• JT-DAC No. 3
• SDS Labs DAC Page

• CD player's Project - information to make and upgrade a CD Player at home

• Electronic bell - Plays 2 mono 8 bit wav files, stored in EPROM
• Heiko's DAT Page - D-7 connections, DAT error counter, SCMS, IR controlling
• Sample Rate Converter Project - inputs an s/pdif (or AES/EBU) signal between 25 and 50kHz, and outputs an s/pdif signal at 44.1kHz

• Audio LED VU meter - built around discrete components
• A-weighting filter
• LM3915 Dot/Bar Display Driver - suitable for VU meters etc.
• LM3916N bar graph driver - data sheet in pdf format, drives a 10 LED bar graph with VU proportions (3dB/step)
• Peak Power Indicator - a very simple circuit for an LED indicator that blinks when the delivered power to the amp exceeds a preset amount
• Peak Reading Level Meter Using Indicator Tubes
• Sound Level Meter - one chip replacement for the standard analog meters, based on LM3915 audio level IC
• VU Meter Amplifier
• VU Stereo Meter - will indicate the volume level of the audio going to your speakers by lighting up LEDs, based on LM3915 IC

• Analog Devices Practical Analog Design Techniques Seminar - seminar papers on web
• Ask the Applications Engineer - a collection of articles from its "Analog Dialog" newsletter in pdf format from Analogue Devices, useful info for people designing ADC and DAC systems
• Analog record and playback IC's
• Circuit Central Library - lots of audio circuits
• Digital Volume Control - based on DS1669 Digital Pot IC
• Dual +/- 15 volt power supply - suitable for powering many opamp circuits
• Guitar Effects FAQ
• Jensen Transformers Application Notes and Schematics
• Known WWW Tube and Audio Internet Sites - check also the second page
• Main principles of amplifier wiring - how to wire operational amplifier circuits
• Mosfet Power Amplifiers - A discussion of the benefits of the lateral Mosfet output devices used in high power audio amplifiers
• Proper Grounding Inside Equipment Avoids Ground Noise Coupling (aka "Pin 1 Problems") - 15KB PDF
• Sheldon's Audio Designs - audio DACs and tube amplifiers
• Subtleties count in wide-dynamic-range analog interfaces - transporting high-dynamic-range analog signals from one piece of equipment to another is not a trivial task, design article from EDN magazine
• Stereo Cassette Player - 150W audio amplifier circuit, complete with stereo pre-head amplifier and bass-treble control section

• Audio circuit at Digital Music Zone - compressors, effects, preamps, microphones, phantom power
• Digital Music Zone Schematics - compressors, microphones and effects
• DIY Audio pages
• Andrea's projects - circuits and documentation

• Abrahamsson Single-Ended amplifiers.
• Ariel Speaker Page
• Audio Engineering Society
• Alan Kimmel's Tube Audio Laboratory
• Audio and Acoustics Internet Sites
• Audio and Hifi
• Audio & Techniek (In Dutch)
• Audio Ideas Guide
• Audio Links
• Audio Review
• AudioWeb Newstand
• Auriga Design
• Black Dahlia Audio Pages
• Campaign Audio Design (cables from the UK)
• DIY Audio Pages
• Entec Homepage
• HEVOS bass amplification. High-end bass amps & cabinets from the Netherlands
• HiFi Notes
• Huge List of Audio Related Sites
• H. H. Moerch - Main
• Kharma / OLS mainpage
• Quad World
• Speakerland / Speaker & Co Home Page
• Stage Accompany website
• StraightWire
• Scandinavian Do-It-Yourself Site
• The Audible Difference LLC - Your High End Audio Connection
• The HiFi pages
• TNT hifi Worldwide
• Tube Sound?
• Ulrich Haumann's Vintage HiFi Pages
• Visions in Audio: a site about high-end audio and music
• VT52 home page

• Antratek Index (Netherlands)
• Chip directory (Netherlands)
• EE Design Center (Questlink Technology) (Login reqd., but it's free)
• Keithley Data Acquistion Products
• Dick Smith Electronics (Australia)
• Doknet (Netherlands)
• Jaycar (Australia)
• Motorola Semiconductor
• National Semiconductor
• Philips Semiconductors
• Sony Electronics
• Van Reijsen Elektronika BV Homepage (Netherlands)
• CadAudio (Denmark) - Speaker distributors (includes small magnetically shielded Audax system, suitable for Hi-Fi PC speaker project).

Index