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Amplifiers: Audio Circuits
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Audio Amplifiers:   #'s       A - D        E - M        N - R      S - U     
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Last Updated: November 30, 2017 10:27 AM

Circuits Designed by Dave Johnson, P.E. :
TV /VCR Remote Range Extender Circuit  -  I often get frustrated by how poor some infrared remotes in many new electronic devices operate.  I used to be able to turn on the TV from 30 feet away.  Now, it seems that I have to get within 15 feet.  To address this issue, I designed the circuit shown below.  The circuit taps into the TV remote’s existing infrared LED and drives 8 more efficient devices.  The result is a communications range some 4 to 5 times longer.   . . . Circuit by Dave Johnson P.E.-October 05, 2005

Video Signal Edge Enhancements  -  I designed this circuit many years ago, based on the claims that the technique would improve the quality of standard TV images.  The circuit adds information to the edges of the objects and was reported to bring out more detail.  After building and testing . . . Circuit by David A. Johnson P.E.-July 08, 2000

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

Spring Reverb -  The Hot Springs tanks and circuit board should be mounted in a location that is free of ambient electro-magnetic fields.  The input and output jacks are typically placed on a patch panel with other effect's inputs and outputs.  In use, the effects or aux send buss of the console patches to the Hot Springs input and the output of the Hot Springs returns to one of the mixer inputs for control of reverb level in the total mix.h __ Contact: PAiA Corporation USA

Spring Reverb Unit for Guitar or Keyboards -  A high performance spring reverb unit for guitar amps __ Designed by Rod Elliott  ESP

Spring Reverberation Module -  Build it and get great concert hall effects for your guitar or keyboard instrument. __ SiliconChip

Stacked Supercapacitor Charger from 1.8V to 5.5V Input to 5V Output (1000mA Max Input Current)  -  The LTC3127 is a wide VIN range, highly efficient, 1.35MHz fixed frequency buck-boost DC/DC converter that operates from input voltages above, below or equal to the output voltage.  The LTC3127 features programmable average input current limit, making it ideal for power-limited input sources.  The input current limit is programmed with a single resistor and is accurate from 0.2A to 1A of average input current. __ Linear Technology/Analog Devices App Note, Mar 24, 2010

Stage & Recording Mixer -  This project is probably the most ambitious so far, and can be expected to be very expensive.  On the positive side, it is also capable of excellent performance, and can be tailored to suit your exact specifications.  There are several different input modules in the series, the first being the microphone and line input. __ Designed by Rod Elliott  ESP

Stage center reverb unit -  Schematic only __ Designed by Craig Anderton

Stereo Audio Amplifier based on TDA2822M -  The TDA2822M IC used in this project is a dual amplifier built  into an  eight pin chip.  It consists of two channels, each identical and with external  components  to  provide  a  very  simple  but  powerful  stereo amplifier, with  a  gain  of  39dB and a current draw of 9mA with supply voltage in the range of 1.815 Volts.  It  will plug into the earphone socket of Walkman type machines and give excellent quality stereo sound from  two  speakers.  Students  are encouraged  to  research  the  fascinating  technology  of  speaker box design. __ CdS Electronic

Stereo Audio Isolator -  This circuit is useful for removing ground loop hum on a remote line level audio signal line.  It can be used to to connect a computer sound card to a stereo amplifier's line input.  Other uses include tapping into a line level signal for powering a remote amplifier, and removing common mode ground interference on 12 Volt audio equipment such as a car stereo.  The circuit can be used in mono applications by simply ignoring the second channel __ Designed by G. Forrest Cook

Stereo audio line driver for running audio over long distance cables -  A stereo line driver for feeding long cables or buffering an audio source. __ Designed by Andy Collison

Stereo audio simulator -  Stereo simulator is used to separate monaural signal between two channels for passing higher and lower frequency.  Here is a circuit of stereo simulator separate the mono signals at two middle frequencies i.e.6 KHz and 250 Hz for providing more pleasant sound.

Stereo Channel Selector -  The add-on circuit presented here is useful for stereo systems.  This circuit has provision for connecting stereo outputs from four different sources/channels as inputs and only one of them is selected/connected to the output at any one time.    When power supply is turned ‘on’, channel A (AR and AL) is selected.  If no audio is present in channel A, __ Designed by G. Forrest Cook

Stereo Class-A Amplifier; Pt.5  -  In this article, we show you how to build a high-performance 20W Class-A Stereo Amplifier using the modules described over the last few months.  The unit will be available as a complete kit from Altronics and the assembly is straightforward. __ SiliconChip

Stereo Electret Microphone PreAmplifier -  The leftmost 10k resistor supplies plug-in-power to the electret, forming part of the FET amplifier in the electret capsule.  This could be anything from 2k to 10k, the higher the better the stereo separation (another mic derives bias from the same rail).  Apparently higher values also lower distortion, and the best bias power circuits involve actually breaking a trace on the electret capsule to allow the use of both a drain & source resistor, but I’m not going that far.  

Stereo Headphone Amplifier -  This is an improved version of headphone amplifier I've built many years ago.  I wanted so much to share it with you because this simple circuit has done a great service

Stereo Headphone Amplifier with LM386 -  After the euphoria over receiving my new Sony Minidisc bundle had partially subsided, I noticed that the portable unit, the MZ-E40, has a rather weak output.  Measurements showed that it can only manage 80mV rms output and only about 74dB SPL output from the phones.  This is when recording at average level with 8dB of headroom.  In contrast, an orchestra __ Stephen H. Lafferty

Stereo jack adds no-cost power/logic control -  EDN-Design Ideas – April 15, 1999    [ NOTE : File has multiple design, scroll for this one.]  Many battery-powered devices use peripherals that require only two conductors to complete their interfaces.  You can use stereo phone jacks and monaural plugs to perform power- or logic-control functions in addition to completing their required I/O connections.  Monaural plugs short-circuit the ring and sleeve of stereo jacks.  You can place the ring connector, normally considered a redundant ground return, into service as an spst switch. __ Circuit Design by Gary O’Neil, IBM Microelectronics, Research Triangle Park, NC

Stereo Line Driver -  A stereo line driver for feeding long cables or buffering an audio source. __ Designed by Andy Collison

Stereo power Audio Amplifier using TDA7297-2 x 15 Watts-Mute & Stand-by optional-Easy to assemble -  complete stereo amplifier circuit including printed circuit board to power of 2 X 15 Watts.  Using minimum of components in the integrated circuit TDa7297 ST Microelectronics.  This IC presents in its interior two bridge amplifiers, making it useful for use where a stereo amplifier need easy assembly.  may operate with voltages 6-18 volts and has […] __ Designed by Antonio Rodrigues

Stereo Preamplifier with Bass-boost -  This preamplifier was designed to cope with CD players, tuners, tape recorders etc., providing a gain of 4, in order to drive less sensitive power amplifiers.  As modern Hi-Fi home equipment is frequently fitted with small loudspeaker cabinets, the bass frequency range is rather sacrificed.  This circuit features also a bass-boost, in order to overcome this problem __ Designed by RED Free Circuit Designs

Stereo Push Pull 3CX300A1 Amplifier -  The schematic is shown HERE.  At some point I will add some detail for this amp, but it is loosely based upon my "Beast" amplifier, referenced elsewhere on this page. __ Designed by Bob Danielak

Stereo tape head preamplifier using LA3161 -  The Stereo Tape Head Preamplifier kit is based on LA3161 IC from SANYO. __ Designed by Rajkumar Sharma

Stereo Test Tone Generator -  This circuit produces two audio frequency sine waves with different frequencies but equal amplitudes.  It can be used for testing a variety of stereo audio equipment.  The circuit was originally developed the purpose of aligning an FM Stereo Modulator, like the type used in low power FM stereo transmitters.  Two tone outputs are available, the low tone has a secondary output that is 180 degrees out of phase with the primary output.  The circuit is also handy for testing computer sound card inputs.  A variety of waveform configurations can be produced by plugging a stereo audio patch cord into the four output jacks. __ Designed by G. Forrest Cook

Stereo Width Controllers -  Sometimes, for a variety of reasons, it would be nice to vary the width of the 'sound stage' when listening to stereo recordings.  Although technically this is anything but hi-fi, it is a useful addition to PC speakers, or even for the music centre in the listening room. __ Designed by Rod Elliott  ESP

Stereovahvistin 2 x 220W RMS -  This is a building plan for an audio amplifier with2 x220-Watt output power.  Text is in Finnish

Stomp Switch wiring -  Stomp Switch wiring __ Designed by Guitar Effect RC Keen

Studio 350 Power Amplifier Module -  Want an audio power amplifier with real grunt? This rugged module is capable of delivering 200W RMS into an 8-ohm load and 350W into a 4-ohm load, at very low distortion. __ SiliconChip

Studio 350 Power Amplifier Module; Pt.2 -  The construction details for this new high-power audio amplifier plus the circuit and wiring details for a matching power supply. __ SiliconChip

Studio Switcher -  Made for Radio Glen at Southampton University, and still in use at the re-named low power AM and web broadcasting station SURGE: Southampton University Radio from Glen Eyre.  Triumph of relay based logic, or unnecessarily retro? You decide.  Nothing with this many illuminated push switches can be all bad. __ Designed by Henry 

Sub Woofer Processor -  Designed to operate a sub-woofer driver below its resonant frequency __ Designed by Rod Elliott  ESP

Subwoofer Equaliser -  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 __ Designed by Rod Elliott  ESP

Subwoofer Filter, Gainer, Auto Power SystE - M -  Schematic only, no circuit description included. __ Designed by © 2003 Lars Clause

Subwoofer for Cars -  This system needs to be attached to an existing car stereo amplifier to add extra 'boom effect' to the music.  It has a dedicated loudspeaker with a power amplifier to boost __ Electronics Projects for You

Subwoofer Phase Control -  A standard phase control for use with subwoofers. __ Designed by Rod Elliott  ESP

Super Mixer -  The mixer described below differs from most mixer circuits in that all the inputs are not only adjustable but fed to a common amplifier which has an adjustable overall gain .  It allows for a weak signal to be amplified and attenuate the other inputs for an even output level of all inputs. __ Contact: © Laurier Gendron, Burnaby, B.C., Canada

Super Spy Transmitter Bug -  A very small home made FM transmitter Bug using a single transistor and with a transmission range of 200 meters.  This FM transmitter Bug is very easy to build.  The size of the circuit board is ONLY 22mm x 10mm.

Supreaux Deux -  The Supro 16T adapted for use as a distortion stompbox. __ Contact: holler @ runoffgroove.com

Surround Processor -  Simple Surround Processor.  This is built with only conventional parts, and digital delay block, too.  So it is very easy to build. __ Designed by The Electronic Lives Manufacturing-presented Chan

Surround Sound Decoder -  This surround-sound decoder is based on the "Hafler" principle, first discovered by David Hafler sometime in the early 1970s.  The original idea was to connect a pair of speakers as shown in Figure 1, for use as the rear speakers in the surround setup __ Designed by Rod Elliott  ESP

S-video to composite video converter -  Some digital TV set-top boxes provide only S-video and component video outputs, which can pose a problem if your TV set only has a composite video inputor you've used up the S-video and component video inputs.  The same can happen with video tuner cards for PCs.  Here's an easy-to-build adapter to get you out of trouble. __ SiliconChip

Switch-mode Power Supply for a Tube Car Amplifier -  To minimize heat loss on any transistor, I use two pass FETs.  In the car, input voltage is either 11.5-12.5V (engine off) or 13.5-14.5V (engine on).  In the first case, T1 and T2 are fully ON, no need for heatsink.  In the second case, T1 is OFF, T2 ON, all voltage and power excess __ Contact: klausmobile @ yahoo.Com

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Audio Amplifiers:   #'s       A - D        E - M        N - R      S - U        V _ Z

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