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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: June 02, 2021 01:44 PM

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 remoteís 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 and designs for engineers, hobbyists, students & inventors:

S/PDIF to Analogue Converter -  This is quite possibly the simplest S/PDIF receiver and DAC available.  It uses the absolute minimum of parts, and also minimises the connections and control functionality usually provided.  It is still a serious project, and is not recommended for beginners __ Designed by Rod Elliott  ESP

Screen-Driven Direct-Coupled Single-Ended EL509/6KG6 Stereo Amp -  The Svetlana EL509/6KG6 is a rugged beam tetrode with a plate dissipation rating of 35W.  It may be classified as a "sweep tube" because it was originally designed as a horizontal sweep amplifier for TV applications.  Its high sensitivity and efficiency allows for up to 15W output from a single tube.  As with any other beam tetrode or pentode, however, distortion in single-ended operation can be high. __ Designed by Bob Danielak

SE 300B Amp -  The schematic for my latest SE 300B amp __ Designed by Bob Danielak

Selection of Integrated Audio Amplifiers -  In a previous article I discussed building audio amplifiers using discrete transistors.  While it is possible to build good audio amplifiers from discrete transistors, they are no match for the many audio amp IC's available to us.  IC's offer many advantages including high efficiency, high gain, low standby current, low component count, small size and , of course, low cost.  It is little wonder that audio amp IC's have replaced discrete transistors in most consumer electronic devices.  While __ Designed by Mike Martell N1HFX

Self tuning CW filter -  It is a narrow band-pass filter,  based upon the LM201 OP-Amp.   The circuit should work using other OP-Amps, but I have not tested this; I only used the LM201. __ Designed by Harry Lythall-SM0VPO

Sensitive FM Transmitter -  Circuit + Parts List + Notes __ Designed by Tony van Roon  VA3AVR

Set Your Lights to Music -  6-Aug-09 EDN-Design Ideas This circuit activates six ac outlets according in a logarithmic thermometer-code format, causing six to 12 strings of lights to flash on and off according to the level and tempo of music you are playing Design by Hanif Saeed, Maxim Integrated Products, Inc, Sunnyvale, CA

Shortwave Bug -  Circuit and notes only, no circuit description given. __ Designed by Tony van Roon  VA3AVR

Signal Detecting Auto Power-On Unit -  The switch detector unit is shown in Figure 1, and uses an LM358 dual opamp, and a handful of other parts.  The relay switching device is a MOSFET, selected because of the almost infinite input resistance.  The 2N7000 shown is recommended because it has a threshold voltage of less than 3V and is fairly cheap, but virtually any MOSFET will work just as well, even if the gate threshold is a little higher.  An MTP3055 can also be used, as shown originally in this circuit. __ Designed by Rod Elliott  ESP

Signal Splitter -  A transformer isolated signal splitter that enables hum-free connection of one guitar to more than one amp as well as having a direct output.  The circuit is buffered to avoid signal loss. __ Designed by Guitar Effect RC Keen

Signature Series Kit Loudspeaker SystE - M -  These new speakers are among the very best kit speakers that money can buy.  They use the very-high-performance Fountek ribbon tweeters and Peerless woofers.  They will be a very good match to our recently described 20W Class-A Stereo Amplifier. __ SiliconChip

Silent Metronome -  File contains several designs, please scroll to find this circuit.  The circuit below is a "silent" metronome that keeps the beat without becoming a member of the band.  The circuit flashes the 6 volt lamp at a rate set by the 20k potentiometer which can have a dial for setting the desired tempo.  Alternately, the potentiometer could be replaced with a rotary switch and selected resistors.  The lamp is an ordinary #47 bulb which will give good omni directional brightness but an LED and resistor could be used insteadtry a 100 ohm in series with a   high-intensity LED.  The batteries could be three C or D cells for good life.  This circuit could be used to generate "clicks" in a speaker but such metronomes are not particularly pleasing.  The ambitious might replace the lamp with a solenoid which taps on the wall of a hardwood box or wooden chime for a "professional" sound. __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Simple 7 band eqalizer -  Audio graphic equalizers are very common as commercial products (for Hi-fi, car audio and stage use) but circuits for them are very rarely published.  I didn't design this one but it's really very simple.  The details shown are for a 7 band but the principle can be extended to almost any number of bandsif you can find accurate enough components. __ Designed by Richard Torrens

Simple Circuit & Small Audio Amplifier -  Extremely Simple and useful for many applications. __ Designed by G.L. Chemelec

Simple Circuit 10W OCL Audio Amplifier with TL081 -  The circuit given below is of a simple audio amplifier that can deliver 12W to an 8 Ohm speaker.  Op amp IC TL081 is used as the preamplifier here.  Actually any opamp with matching power supply ratings can be used instead of TL081.  Transistors Q1 and Q2 (TIP125 and TIP120) comprises the power amplifier stage.  Output is taken from the collector junction of two transistors

Simple Circuit Audio preamplifier -  This is a very easy circuit to buildall parts can be found at the local electronics shopno matter how worthless it (the local shop,) usually is. __ Designed by Andy Wilson

Simple Circuit Audio Tone Control -  This very simple passive circuit provides a simple audio shaping function. It was described by Derek Bowers in Electronic Design in February, 2012. __ Designed by Bob Cromwell

Simple Circuit Bass Guitar Compressor -  An ultra simple compressor, ideally suited for bass guitar. __ Designed by Rod Elliott  ESP

Simple Circuit Class a Amplifier-10W audio output -  This page describes an antenna, a 1 watt final output stage, and a transformation network for radio experiments at 187 kHz __ Designed by J. L. Linsley Hood, M.I.E.E.

Simple Circuit Color Organ -  A simple, satisfactory Color Organ can be built with a handful of cheap components.  This design features: no mains supply transformer, built-in microphone and three widely adjustable frequency bands obtained by means of very simple, passive filters for Bass, Middle and Treble __ Contact: Flavio Dellepiane, fladello @ tin.it

Simple Circuit Colour Organ -  This is a simple, one lamp colour organ.  It is far less complicated then the Three Channel Colour Organ.  It is simply a lamp controlled by an SCR.  It can be built in a few minutes, and combined with other circuits to make some pretty neat effects. __ Designed by Aaron Cake

Simple Circuit Current Feedback Power Amplifier -  The amplifier shown here was previously incorrectly referred to as 'El-Cheapo'.  Thanks to a reader who had a copy of the original 1964 article, it was immediately obvious that my recollection was flawed in the extreme. __ Designed by Rod Elliott  ESP

Simple Circuit High Quality Hi-Fi Preamp -  As it says, simple, high quality preamp.  Has all the facilities normally expected __ Designed by Rod Elliott  ESP

Simple Circuit Line Mixer -  The circuit is an audio mixer circuit so simple as it can be.  There are two dual logarithmic potentiometers in the circuit to adjust the input signal levels and some resistors to do the actual mixing.  The circuit is totally passive, so no power supply is needed.  The circuit is suitable __ Designed by Tomi Engdahl

Simple Circuit LM386 Audio Amplifier -  This simple amplifier shows the LM386 in a high-gain configuration (A = 200).  For a maximum gain of only 20, leave out the 10 uF connected from pin 1 to pin 8.  Maximum gains between 20 and 200 may be realized by adding a selected resistor in series with the same 10 uF capacitor.  The 10k potentiometer will give the amplifier a variable gain from zero up to that maximum. __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Simple Circuit megaphone 9 Volt -  Schematic only

Simple Circuit metronome using LM1458 -  No circuit description, schematic only __ CdS Electronic

Simple Circuit microphone preAmplifier #2 -  This is a simple microphone preamplifier circuit which you can use between your microphone and stereo amplifier.  This circuit amplifier microphone suitable for use with normal home stereo amplifier line/CD/aux/tape inputs.  This microphone preamplifier can take both dynamic and electret microphone __ Designed by Tomi Engdahl

Simple Circuit MIDI tester -  Sometimes when experimenting with different soundcards and MIDI interfaces it is useful to see if there is some data going in MIDI interface.  This can be easily tested with this adapter, which converts the midi signals to visible light pulses.  Just the circuit and plug it to the MIDI output of your computer.  When computer sends any midi data out, you see the LED flashing.  I found this tester very useful in testing homebuilt soundcard MIDI interface. __ Designed by Tomi Engdahl

Simple Circuit Mixer 3 Input -  This is the very simple 3 input mixer for your audio system.  You can add the number of input by adding some components for mixer input (P=10K R=22K).  This circuit is only recommend for low and intermediate audio sound system.  You need better mixer circuit for your high class audio system.

Simple Circuit open source MP3 player with SD/MMC memory card support -  This is basically a crystal radio with an audio amplifier which is fairly sensitive and receives several strong stations in the Los Angeles area with a minimal 15 foot antenna.  Longer antennas will provide a stronger signal but the selectivity will be worse and strong stations may be heard in

Simple Circuit 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 Iím not going that far.  

Simple Circuit 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

Simple Circuit 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

Simple Circuit Symmetrical MOSFET Audio Amplifier -  High QualityHigh power: 75W into 8 Ohm load.  Fully symmetrical configuration __ Contact: Flavio Dellepiane, fladello @ tin.it

Simple Circuit Timer Remembers Your Rhythm -  01/05/95 EDN-Design Ideas The unpretentious controller in Fig 1 remembers the interval between your pressing its start and stop buttons.  Thereafter, the controller switches the load on and off every day at the same times as you did.  You reset the controll Design by MS Nagaraj, ISRO Satellite Centre, Bangalore, Karnataka, India

Simple Circuit to Connect Telephone Equipment to Audio Mixer -  I have used this type of circuits for quick testing of telephone equipment.  This is a quick hack that does not exactly resemble the characteristics of the real telephone network, but is enough for this kind if applications.  If you want better simulation, change the resistor to 600 ohm and increase the power supply voltage.  And by the way __ Designed by Tomi Engdahl

Simple Circuit Transistor Organ -  This simple circuit can provide hours of enjoyment as you learn tunes, play duets or just make some really weird sounds by pushing all the buttons at once.  You have probably seen this circuit before, it is fairly common.  I have seen it in several __ Designed by Aaron Cake

Simple Circuit Two Line Output Combiner -  Sometimes there is need to combine the output of two line level audio sources to be fed to one input.  A standard way in professional audio is to use a mixing desk, but on home audio system you might want to look for a simpler and less expensive alternative.  Some people have suggested of combining two audio outputs with an "Y-adapter" which is ment to split one output.  Those adapters are just one male connector and two feamle connector directly wired to each other in the followin way: __ Designed by Tomi Engdahl

Simple Circuit Valve Amplifiers -  A collection of economical low power amplifier designs using common low cost valves. __ Contact: blehack @ yahoo dot com

Simple Circuit Wireless Microphone -  This wireless FM microphone is simple to build and it has a useful transmitting range (over 300 meters in the open air).  Despite its small component count and a 3V operating voltage it will easily penetrate over three floors of an apartment building.  It may be tuned anywhere in the FM band (87-108MHz) and its transmissions can be picked up on any standard FM receiver. __ hobbyteam @ hobby-hour.com

Simple FM Transmitter -  There is no thrill like the thrill you get from operating equipment you have built yourself.  If you have never built a project from a magazine before, let this be your first--you'll see how much satisfaction and fun you can have! __ Designed by Tony van Roon  VA3AVR

Simple IF Amplifier -  I wanted to replace the 150-kHz ceramic IF filter a Kenwood KT-880D used in narrow-IF mode with two Murata 110-kHz filters. I needed an amplifier to compensate for the additional loss and to isolate and properly terminate the filters. __ Designed by Brian Beezley K6STI

SIMPLE LF PRE-AMP (Basics) -  Circuit conly __ Designed by Guy Roels ON6MU

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