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Audio Schematics - Audio Accessories

120VAC Touch Switch - This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load.

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

2-Way Electronic Crossover - Conventional 3rd order electronic crossover

24 dB/Octave 2/3-Way Linkwitz-Riley electronic crossover - Linkwitz-Riley alignment. This is a very nice crossover, Rev-B boards now available

3 Channel-Color Organ - This is an excellent item for parties, dances, etc. The circuit is based on an Integrated Circuit which provides three sharp active filters for each channel. Three independent controls vary the amount of light for low, midrange and high frequencies.

3 Level Audio Power Indicator - Battery-operated3 LED display that connect it to loudspeaker output

3-Way 12dB/ Octave Crossover - Contributed project, simple 12dB/ Octave crossover network.

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

48V Phantom Supply - Low noise 48V regulator and phantom mic supply circuits.

A DC-Coupled, Selectable-Gain Headphone Amplifier - This design uses two opamp gain stages per channel for superior input buffering and a discrete bipolar output stage with thermal tracking current mirrors. The amplifier's overall gain can be adjusted to match the efficiency and impedance characteristic of any headphone.

A Musical Distortion Primer - This is an introduction to the basic means of distorting a signal in a musically useful way. The approach is as non-technical as possible.  I use the simplest signal waveform, a sine wave, to illustrate all these, although a guitar is much more like a sawtooth than a sine wave. The clipped waveforms will be shown in their raw state

A Reader's Xover - This is well worth reading if you can't decide on biamaping

A Soundfield Simulator for Stereo Headphones - An adaptation of the Linkwitz acoustic simulator (see An Acoustic Simulator for Headphone Amplifiers by Chu Moy above) as a front-end for headphone amplifiers with very high input impedance, such as the author's own headphone amp project (see A DC-Coupled, Selectable-Gain Headphone Amplifier). This circuit features a continuously adjustable Soundfield control.  Designed by Chester Simpson

A-B Switch Box - Can you really hear the difference between amps or cables?

ABX Comparator - Full ABX testing unit, without microcontrollers or a PC

Active Subwoofer & Controller

Add headphones to a Class D Amplifier - EDN  Connect headphones to the MAX9704 and make a quieter lab or office

Add on Stereo Channel Selector

Amplificateurs audio - en Français

Amplifier Phono Input as Line Level Input

Amplifier Thermal Protection

An Equalization Circuit for the beyerdynamic DT990 Pro Headphones - This passive EQ corrects a rising characteristic in the frequency response of the beyerdynamic DT990 Pros and turns them into one of the most natural and accurate sounding headphones on the market.  Designed by LXH2

AN215: CS4201/CS4202 Headphone Jack Sensing using GPIO

Korg Releases Monotron Synth Schematic

Anti-RIAA Equalizer for Line to Mag Phono Converter - AS071 Jenson Transformer Application Note 

Arc welder sound simulator

Audio Amp Output Power Limiter

Lap Timer Part 5 - Buzzer, External Audio and Some Builds

Audio Amplifier Output Relay Delay - This is a simple circuit which I built to one of my audio amplifier projects to control  speaker output relay. The purpose of this circuit is to control  relay which turns on  speaker output relay in  audio amplifier. The idea of  circuit is wait around 5 seconds after  power up until  speakers are switched to  amplifiers

Audio Auto Shutoff  - The purpose of this circuit is to automatically turn off any device plugged into its power outlets after a certain period of time. Shutoff is activated by an absences of an audio signal or by a standard timer function. This unit would be connected to speaker terminals of a stereo system, tape outputs, TV earphone jack or audio outputs etc. Once the audio signal drops below a predetermined level

Audio Detector Circuit

Audio Graphic Equaliser - Simple 7 band eqalizer

Audio Level Meter - The circuit has a flat frequency response from about 20Hz to well over 50Khz. Input sensitivity is 100mV for a full scale deflection on a 100uA meter. Built on two common emitter amplifiers, the first stage has a preset resistor which may be adjusted for a FSD.

Isolation Shield System

Audio Line Isolator #1

Audio notch filer

Audio Peak Reading Meters

Audio test accessory isolates & matches loads - EDN-Design Ideas: This low-cost, switchable, dual-impedance transformation circuit comprises a single conventional transformer and two minimum-loss pads.

Audio Test Oscillator - As a piece of test equipment, an audio oscillator has to be considered essential for anyone working in with hi-fi gear. Together with an audio millivoltmeter (as described in Project 16), and even better if you have access to an oscilloscope, you will be able to make proper measurements on everything from preamps, RIAA equalisation stages (for vinyl disks), tone controls, crossover networks, etc.

Audio Quality Output Transformers

Audio Voice-Over Circuit

Audio VU Meter - LM324, This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324

Auto Shut-Off for Cassette Players & Amplifiers

Auto volume control

Automatic Charger for Battery Operated Hi-Fi Preamps

Automatic Loudness Control - Simple add-on module Switchable "Control-flat" option

Balanced Audio Input Circuit - 109KB PDF file

Balanced Line Driver & Receiver - Use these to eliminate hum for long signal leads

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

Bluetooth Headset - Intersil Application Block Diagram

Bridging Adapter for Power Amplifiers

Buffered Headphone Driver/Preamplifier - With a fast Motorola buffer as its only active circuitry, this design specifies the highest quality parts and careful construction to avoid signal coloration. The author includes instructions for substituting other buffer ICs.  Designed by Eldon Pawliw

Build These Noise-Canceling Headphones (plus: Binaural Mike Headset, Audio Probe & Parabolic Mike) - Muzzle the din and relax to the sound of silence with headphones that combat the uproar with "anti-noise." The author includes modifications for a binaural microphone headset, an audio probe and a parabolic microphone.  Designed by Jules Ryckebusch

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