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Audio Circuits:  Audio Accessories Page 1
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Last Updated on: Monday, October 03, 2011 06:07 PM

Circuits Designed by Dave Johnson, P.E. :
  • 120VAC Touch Switch
    This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load.  (added 12/04)

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

120VAC Touch Switch -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load.... [Designed by David A. Johnson]
2 Line Output Combiner -  Convert consumer equipment stereo signal to mono or combine audio signal from two different equipments to1-input (added 4/02)
24 dB/Octave 2/3-Way Linkwitz-Riley electronic crossover -  Linkwitz-Riley alignment.  This is a very nice crossover, Rev-B boards now available (added 05/06/07)
2-Way Electronic Crossover -  Conventional 3rd order electronic crossover (circuit added 6/07)
3 Channel-Color Organ -  An old ideabut I've had numerous requests for a good design for this....(electronic schematic added 12/08)
3 Level Audio Power Indicator -  Battery-operated3 LED display that connect it to loudspeaker output (added 04/02)
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 (added 4/02)
300 Watt Subwoofer Power Amplifier -  (schematic added 9/02)
3-Way 12dB/ Octave Crossover -  Contributed project, simple 12dB/ Octave crossover network. (added 05/06/07)
48V Phantom Supply -  Low noise 48V regulator and phantom mic supply circuits. (added 05/06/07).
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. The author provides detailed instructions for optimizing the....Designed by Chester Simpson  (Circuit design added 04/05/06)
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....(Circuit design added 04/05/06)
A Reader's Xover -  This is well worth reading if you can't decide on biamping (added 6/07)
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  (Circuit design added 04/05/06)
A-B Switch Box -  Can you really hear the difference between amps or cables? (circuit added 6/07)
ABX Comparator -  Full ABX testing unit, without microcontrollers or a PC (circuit added 6/07)
Active Subwoofer & Controller -  (schematic added 9/02)
Add headphones to a Class D amplifier -  9-Jul-09 Issue of EDN  Connect headphones to the MAX9704 and make a quieter lab or office.... [Design Idea by Hiroshi Fukushima, Technical Research Center, D&M Holdings Inc, Kawasaki City, Kanagawa, Japan]
Add on Stereo Channel Selector -  (electronic Circuit / Schematic added 10/04)
Amplificateurs audio -  en Français (added 08/08/08)
Amplifier Phono Input as Line Level Input -  (electronic schematic added 8/02)
Amplifier Thermal Protection -  (schematic added 9/02)
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 -  (app note added 6/07)
Analog Synth Keyboard Schematic -  (electronic circuit added 2/07)
Anti-RIAA Equalizer for Line to Mag Phono Converter -  AS071 Jenson Transformer Application Note  (app note 6/07)
Arc welder sound simulator -  (diagram added 2/07)
Audio Amp Output Power Limiter -  (schematic added 9/02)
Audio Amp Timer -  Turns-off your amplifier when idle for15 minutes Fed by amplifier tape-output (added 9/04)
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....  (added 11/05)
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 a …. [Randy Linscott]
Audio Detector Circuit -  (diagram added 2/07)
Audio Graphic Equaliser -  Simple 7 band eqalizer (diagram added 2/07)
Audio Level Meter -  Audio levels can be monitored using a small panel meter with this circuit built from discrete components.  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. The last stage is biased to operate at roughly half the supply voltage for maximum ac voltage swing. Audio frequencies are passed through the 10u dc blocking capacitor and the full wave bridge rectifier converts the signal to a varying dc voltage....(schematic design added 01/2010)
Audio line isolator -  (electronic circuit added 2/07)
Audio Line Isolator #1 -  (electronic circuit added 1/03)
Audio Line Isolator #2 -  (electronic schematic added 8/02)
Audio notch filer -  (electronic circuit added 2/07)
Audio Peak Reading Meters -  (circuit added 7/02)
Audio Signal Source -  (diagram added 2/07)


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