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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:

Simplest Ever Amplifier Bridging -  A design for a simple add-on bridging adapter for stereo power amplifiers __ Designed by Rod Elliott  ESP

Simplified Audio Amp Model -  (spice design) __ Designed by Rick 

Singing Christmas tree based on Microchip PIC16F84 -  Microcontroller based electronic circuit __ Designed by Aleksander Stare

Single Amplifier 4 Band Passive EQ -  Schematic Only __ Contact: info @ forsselltech . com

Single capacitor powers audio mixer -  03/14/97 EDN-Design Ideas Micro power and low-voltage op amps allow you to build high-performance analog-signal processors that require no batteries or wall transformers, __ Circuit Design by Aleksandr Belousov, Rego Park, NY

Single Chip 50 Watt/8 Ohm Power Amplifier -  Uses National Semiconductor LM3876 Power IC.  Voltage gain is 27dB.    Voltage gain is 27dB as shown, but this can be changed by using a different value resistor for the feedback path (R3, currently 22k, between pins 3 and 9).  The inductor consists of 10 turns of 0.4mm enameled copper wire, wound around the body of the 10 Ohm resistor. __ Designed by Rod Elliott  ESP

Single Ended 5687 Amplifier -  Single Ended 5687 Amp and power supply schematics, only, for now. __ Designed by Bob Danielak

Single Ended Class A2 SV811 10 Stereo Amp -  This project actually began its life as a Single-ended 211 design.  I received the Parts Connection Catalog just before Christmas (1995).  In the back were the data sheets for various tubes, including the lovely 211.  I had been hearing a lot of good things about this tube, so I started pokeing around. __ Designed by Bob Danielak

Single supply op-amp audio Amplifier -  I am trying to create an op-amp amplifier that would work from single 5V supply, and would be able to amplify -100mV to +100mV audio signal to around a 1V peak-peak or so.  I've came across this circuit from this article, that could seem to work, but am having trouble calculating the actual values

Single-Ended 2A3 Amp -  This amp uses a 6C45pi input tube loaded by a 1:1 Interstage Transformer (I used the inexpensive model available from Allied Electronics).  The 6C45pi is supposedly not rated for more than 200V on the plate, but I have not had any trouble with 300V in this application.  You may not wish to follow in my footsteps if you paid a lot for your 6C45pi's __ Designed by Bob Danielak

Single-ended driver for a Circlotron OTL -  Originally, this circuit was driving a 6B4G PP output stage.  Transformer-coupled, naturally.  I started with cap-coupled Mullard splitter using three 4P1L direct-heated loktal pentodes.  Not bad at all, but had insufficient gain.  Then I tried a plain Loftin-White configuration with a LL1660 interstage (this one is a one-of-a-kind custom 30mA version __ Contact: klausmobile @ yahoo.Com

Siren 100dB -  This is a very loud siren and if two or more piezo's are located in a room, the burglar does not know where the sound is coming from. __ 555-Timer

Six Channel Mixer & Amplifier -  One of my most ambitious projects, this mixer was made for my friends Tony and Wilfred of Mixed Fruit Jam as a practice amp.  It's a relatively straightforward design, and will probably not be the best way of doing this.  However, it works fairly well, and is relatively inexpensive to build. __ Designed by Tony and Wilfred of Mixed Fruit Jam

Small Amplifier -  Here is a simple and humble mini 2W amplifier suitable for small pocket radios and other portable audio gadgets.  The circuit is based on Phillips Semiconductors IC TDA 7052.  The amplifier can be run even from a 3V Mercury button cell.  This makes it ideal for battery operated gadgets

Soft Start for Power Amps -  Although the soft start circuit can be added to any sized transformer, the winding resistance of 300VA and smaller transformers is generally sufficient to prevent a massive surge current.  Use of a soft start circuit is definitely recommended for 500VA and larger transformers __ Designed by Rod Elliott  ESP

Soft Switching Amplifier with Tone Controls -  Built around an LM380, this amplifier includes tone controls and electronic "soft switching".  The soft switching circuitry ensures power is built up gradually eliminating the dc thump __ Designed by Andy Collison

Solid State Power Op-Amp Amplifier -  LM675 Amp Schematics, only.  This was my minimalist interpretation of the so-called "Gaincard" amplifier.  It uses the minimum number of parts I could get away with.  All parts are directly soldered to the IC leads for minimal stray inductance.  It works and sounds suprisingly good! __ Designed by Bob Danielak

Solid-state Fender Blackface Preamp -  All-FET version of the celebrated valve guitar preamp; Can be easily modified to Marshall Tone Controls specs __ Contact: Flavio Dellepiane, fladello @ tin.it

Song Number Display -  Here’s a circuit to display the song number in an audio system for quick reference to songs.  It also serves the purpose of an extra visual indicator in modern audio systems.When __ Electronics Projects for You

Sound Activated Relay #1 -  This relay remains dormant until the op-amp activates upon sound via the electret-microphone.  I only tested the 2-wire type.  The input stage is a regular off-the-shelf 741 operational amplifier and connected as a non-inverting follower audio amplifier. __ Designed by Tony van Roon  VA3AVR

Sound Activated Relay #2 -  This relay remains dormant until the op-amp activates upon sound via the electret-microphone.  Only tested with the 2-wire type.  The input stage is a regular off-the-shelf 741 operational amplifier and connected as a non-inverting follower audio amplifier __ Designed by Tony van Roon  VA3AVR

Sound Card with PCM2702 -  Make a sound card is no more a complex issue.  If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card.  This sound card can be

Sound Controlled Flip Flop -  Described here is a very inexpensive solution to many phono-controlled applications like remote switching on, for instance, or activating a camera, tape recorder, burglar alarms, toys, etc.  The circuit given here employs a condenser microphone as the pick-up.  A two-stage amplifier built around a quad op-amp IC LM324 offers a good gain to enable sound pick-up upto four metres.  

Sound Detector -  for use with the sound detector circuit/electret mike amplifier.  when the 555 IC goes into timing mode (triggered by an output signal from the sound detector amplifier,) the timer's output (pin 3) is set into HIGH for a duration set by C2, and R2.  adjusting R1 will adjust how long it listens, from __ Designed by Andy Wilson

Sound Detector tone Decoder -  The bat ultrasounds are picked up by the microphone SPKR1 and go through two stages of amplification at Q1 and Q2.  Separately, a tunable (R12) single frequency is produced by the LM567 oscillator U1.  The LM567 is a tone decoder but here its input is grounded and its voltage controlled oscillator is used as a precision oscillator __ Designed by New Jersey chapter of the Society for Amateur Scientists

Sound Level Meter -  One chip replacement for the standard analog meters, based on LM3915 audio level IC. __ Designed by Aaron Cake

Sound Modifier -  Four shape-controls portable unit; Wide variety of output waveforms __ Contact: Flavio Dellepiane, fladello @ tin.it

Sound Operated Switch -  This circuit must have a 5v regulated supply.  This is provided by the 7805 regulator.  The circuit shown above should be sensitive enough to respond to a reasonably loud clap of the hands at a distance of about a metre from the microphone.  If the microphone (loudspeaker) is not very close to the circuit board, use screened lead to connect it to the rest of the circuit.  If you require greater sensitivity, you can add the simple pre-amp shown below. __ Designed by © David Hoult

Sound pressure level meter -  Suitable for home-cinema setup;  9 Volt operated portable unit __ Contact: Flavio Dellepiane, fladello @ tin.it

Sound Activated Switch -  this was connected to a battery powered mobile which activated when a baby cried __ Contact: P. Townshend EduTek Ltd

Spartacus AO-44 Guitar Slave Amp -  small push-pull tube amp __ Designed by G. Forrest Cook

Spatial Distortion Reduction Headphone Amp -  The schematic in Figure IV is a prototype circuit that implements the required frequency and crossfeed contouring.  As a development objective, the low and high frequency contouring and crossfed control elements must not interact-they must be independently adjustable __ Designed by © John Conover

Speaker cabinet simulator-professional-quality frequency response in a DIY-friendly -  A professional-quality 4x10 open-back speaker cabinet simulator. __ Contact: holler @ runoffgroove.Com

Speaker Protection -  The circuit protection output of power amplifiers and loudspeakers, dispose certain interesting elements, as the isolation of loudspeakers from the exit of amplifier, when is presented continuous voltage in his exit or when the temperature of heatsink, goes up excessively, providing simultaneously and time delay in the connection loudspeakers in the amplifier, so that we avoid pass in them, the known annoying noises from the charge, discharge of capacitors of supply.  

Speaker Protection & Muting -  Protect speakers from turn-on and turn-off transients and amplifier faults __ Designed by Rod Elliott  ESP

Speaker signals to line level inputs -  The circuit is designed to work with typical HIFI amplifiers where negative speaker connector (black) is connected to amplifier ground.  Be careful here because some modern amps have both terminals actively driven.  Connecting either one to a common reference could cause the output stage to smoke __ Designed by Tomi Engdahl

Speech Amplifier Box -  Small portable device6V battery operation;  Suitable for teachers, lecturers, tourists' guides etc. __ Contact: Flavio Dellepiane, fladello @ tin.it

Speech Amplifier by TDA7052 -  This circuit given here can be housed in the box containing the speaker to form a handy microphone amplifier.  The device can be used by teachers, guides, lecturers etc for speaking in a crowdy or noisy environment.  The circuit is designed base on the audio power amplifier IC TDA 7052.  The IC can deliver a maximum power output of 1.2 W at a 6V supply

Splitter-Blend -  The Splitter-Blend provides two buffered parallel effects loops with a Blend control.  Also, a phase polarity switch is included to allow phase matching of the effect loops.  Possible uses are blending two sets of effects placed in the loops, a signal splitter, a simple mixer, or to blend an effect with the dry signal.  The phase inverter can be used for interesting results when mixing dry and effected signal. __ Contact: holler @ runoffgroove.Com

Spot-frequency Sine Wave Generator -  300Hz, 1KHz, 3KHz "output stable" test equipment tool.9V battery powered portable unit __ Contact: Flavio Dellepiane, fladello @ tin.it

Spreadsheet converts sound levels -  05/12/05 EDN-Design Ideas Calculate sound level versus source distance __ Circuit Design by Dan O'Brien, Mallory Sonalert Products Inc, Indianapolis, IN

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