2 Channel Noise Gate:

2 Line Output Combiner: Convert consumer equipment stereo signal to mono or combine audio signal from two different equipments to1-input

3 Channel Spectrum Analyzer: This3 channel15 LED spectrum analyzer can be used as an addition to any audio amp project. It produces fantastic displays on three LED bars that can be individually adjusted for any particular frequency range.

30 DDm to +30 DDm Audio Level Meter: circuit with balanced input and adjustable gain to drive needle type VU meter, uses special amplifier module from Op-Amp Labs

300 Watt Subwoofer Power Amplifier:

Acoustic Simulator for Headphone Amplifiers: a simple RC filter that creates a more realistic sound image in headphones by electronically mimicking spatial hearing with "shaded" interchannel cross feed

Active Subwoofer & Controller:

Active Subwoofer:

Add On Stereo Channel Selector:

Amplified Ear:

Amplifier Phono Input As Line Level Input:

Amplifier Thermal Protection:

Anit RIAEqualizer for Line to Mag Phono Converter:

Audio Amp Output Power Limiter:

Audio Amp Timer: Turns-off your amplifier when idle for15 minutes Fed by amplifier tape-output

Audio Amplifier Output Relay Delay: Audio Amplifier output relay delay

Audio Auto Shutoff: purpose of this circuit is to automatically turn off any device plugged into its power outlets after a certain period of Time of silence

Audio Level Meter:

Audio Line Isolator #1:

Audio Line Isolator #2:

Audio Peak Reading Meters:

Audio Transformer #1: application note article on audio transformers

Audio Transformer #2: notes on using audio transformers for balanced signal interfacing

Audio Trigger Circuit for Lamp Chasers: works with almost any light sequencer circuit with clock input, better working beat sync than in many commercial light controllers

Audio VU Meter:

Auto Shut off for Cassette Players & Amplifiers:

Balanced Audio Input Circuit: 109KB PDF file

Bass Beat Extractor: an automatic gain control circuit followed by a low pass filter, converts the beat into a sharp pulse suitable for triggering the strobe or chaser

Bridging Adapter for Power Amplifiers:

Building the L R Test Set: helps you to set up left/right channel balance on audio broadcasting systems

CD ROM Drive As Digital Audio CD Player:

Color Organ #1: make different colored bulbs light at different frequencies of music, connects to speaker outputs

Color Organ #3: makes3 Light to blink and flash to music

Compressor using Photo Resistor: very basic circuit based on LED, LDR and Op-Amp

DC Fault Protection Circuit for Audio Amplifiers: Circuit ideas how to replace traditional CD protection relays with MOSFETs

Designing a Limiter for Headphone Amplifiers: review of diode-based limiter design, HeadWize

Digital Echo Unit: mono unit for producing special effects for amateur dramatics

Digital Echo:

Direct Injection Box for Recording & PSystems: passive and active DI-box designs

Distortion Analyser:

Dynamic Range Processor: this stereo unit allows the dynamic range of a signal to be increased expansion or decreased compression by a variable amount up to 3:1, based on the SSM2120 dynamic range processor IC

ESP SIM Sound Impairment Monitor): a method of determining just how much your amplifier modifies the original signal

Fast Audio Peak Limiter:

Guitar Effect Circuit #1:

Guitar Effect Circuit #2: Wah, Fuzz and sustain 

Guitar Effect Circuit #3: this is an Aaron Cake circuit -we are linking directly to ACs site.

Guitar Reverb Pedal:

Guitar Tremolo Unit:

Guitar Vibrato Unit:

Hand Clap Electronic Control: turn relay on and off by hand Clap

Headphone Amplifier #1:

Headphone Amplifier #2:

Headphone Amplifier #3:

Headphone Driving Circuit for Soundcards:

High Quality Intercom:

Highresolution Volumeunit Meter Simplifies CD Recording: 06/21/01 EDN-Design Ideas /  PDF contains multiple circuits - scroll to find this circuit.

Hornet Fuzz Box:

Infrared Cordless Headphone:

Infrared Head Phones: Using this low-cost project one can reproduce audio from TV without disturbing others. In place of a pair of wires, it uses invisible infrared light to transmit audio signals from TV to headphones. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS.

Infrared Theremin Musical Instrument:

JLH Headphone Amplifiers:

Kumisa Mk. II Headphone Amp: DIY headph1-amplifier project using AD844 and some special transistors

Light Organ for Car: flashes3 low voltage Light, operates at10-25-Volt voltage, in PDF format, text in Finnish

linkwitz Cosine Burst Generator: part of speaker measurement set described in the construction article

Load Sensing Automatic Switch: apply power to the entire audio system by turning on1-item, simple circuit

Loudspeaker Protection & Muting:

Magnetic Cartridge Amplifier:

Making Differential Probes: For sensing audio signal voltages across devices that are not ground referenced

MIDI Passthrough Circuit:

MIDI Tester:

Mixed Feedback Drive  for Audio Output Transformers: Using feedback eliminates transformer distortion and primary resistance

NHT Subwoofer Amp:

Not Just Another Headphone Amp: battery-powered musicians practice and monitoring amplifier for guitar

One Transistor Theremin:

Parametric & Subwoofer Equalizer:

Peak Reading Audio Level Meter: indicates peak audio response on an analogue meter, similar to a tape recorder recording level meter

Pocket Equalizer for Headphone: many circuit examples

Pocket Headphone Amplifier: portable headph1-amplifier for testing purposes using Burr-Brown OPA132 Op-Amp in a non-inverting configuration, powered with 9V battery

Portable headphone Amplifier:

Pre Distortion Techniques: Tape Linearizer and a Distortion Analyzer

Precision Audio MilliVoltmeter: Measures10mV to50Volt RMS in eight ranges Simply connect to your Avo-meter set @50µA range

Q&D Compressor #2: based on SSM2166

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: One-LED monitors3-levels:50, 70 & 85 dB

ScanMate Audio Activated Recorded:

Shunt Capacitance Can Suppress Magnetic Headset Oscillation : 09/02/02 Electronic Design - Ideas for Design / The nominal impedance of a magnetic headset isn't necessarily a good description of its actual impedance as a function of frequency. A headset's fairly complex equivalent circuit may even lead to parasitic oscillations in a driving amplifier. But...  

Sound Detector:

Sound Operated Switch:

Speaker Protector:

Speaker Signals to Line Level Inputs:

Spyder An Eight Output Pedalboard Power Supply: Outputs regulated 9V DC

Stereo Broadcast Limiter: Circuit for the Ramsey FM10a/FM25 Transmitter

Stereo Compressor #1:

Stereo Compressor #2:

Stereo Compressor #3:

Stereo Width Controllers:

Subwoofer Equalizer: The Linkwitz transform circuit is a hugely flexible way to equalize the bottom end of a sealed loudspeaker enclosure. A speaker that is corrected using this method is flat from below resonance to the upper limit of the selected driver. The low frequency roll off point is determined by the parameters of the transform circuit. Should the enclosure size be too small and cause a lump in the response before roll off, this is also corrected. A conventional active crossover network is then used to divide the subwoofer signal from the main channel signals. Note that there is also a separate spreadsheet calculator available for calculating component values for different situations not handled by the original circuit.

Subwoofer Filter: 12 dB/octave low pass filter for subwoofer, includes subsonic filter

Telephone Headgear: A compact, inexpensive and low component count telecom head- set can be constructed using two readily available transistors and a few other electronic components. Since the circuit draws very little current, it is ideal for parallel operation with electronic Telephone set. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS.

Telephone Record Control:

Telephone Recorder #1: This circuit lets you record your ph1-conversations automatically, notice that this circuit does not provide isolation between Telephone line and the recorder

Telephone Recorder #2: This circuit automatically records all incoming and outgoing phone-conversations with an ordinary cassette or tape recorder. The circuit below distills the audio signal from the phone-line and automatically starts/stops the cassette recorder.

Telephone Recording Circuit #1:

Telephone Recording Circuit #2: How they work and some example 

Telephone Tap #1: Amplify or record a telephone call with the simple circuit shown. The 8-W secondary winding of a miniature transistor output transformer is connected in series with either of the telephone lines. The1000-W primary winding can feed either a cassette recorder or an audio amplifier.

Theremin Model #145:

Three Channel Spectrum Analyzer: This Three channel15 LED spectrum analyzer can be used as an addition to any audio amp project. It produces fantastic displays on three LED bars that can be individually adjusted for any particular frequency range.

Tone Detector:

Tone Generator:

Transistor Organ:

Truth About Vocal Eliminators: Sometimes a vocal can be removed almost completely, but just as often the results are disappointing, just information without circuit diagrams

Tube Active Crossover:

Two Channel Noise Gate:

Two Line Output Combiner: Convert consumer equipment stereo signal to mono or combine audio signal from two different equipments to1-input

Use Multiplier Core for FM Stereo Multiplexed Transmission System : 09/02/02 Electronic Design - Ideas for Design /  A versatile four-quadrant analog multiplier core from Analog Devices, the AD633, is widely used in applications like modulation and demodulation, automatic gain control, power measurement, and voltage-controlled amplifiers. This wide spectrum of...  

Voice feedback enhances engineering calculator: 07/11/2002  EDN - Design Ideas /   The screen shot in Figure 1 represents a Microsoft Excel 2002 worksheet designed to implement VFI (voice-feedback interface) for an engineering calculator. The voice-interface technique has both practical and educational aspects. It automates the common task of finding the values of two resistors for a given ratio..

Voice Over Circuit: Switches automatically from sound source to microph1-when enough sound comes in from microphone.

Warbler:

Weighting Filter for Audio Measurements:

Wein Bridge Theremin:

What Compressor: The What Compressor is a super transparent vocal and instrument compressor that you can build.

Wireless IR headphone Receiver:

Wireless IR headphone Transmitter: