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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: December 25, 2017 01:42 PM

Circuits Designed by Dave Johnson, P.E. :

Pop Free Microphone On/Off Switch Circuit  -  This circuit uses a simple technique to eliminate the usual “pop” sound when an electret type microphone is switched on or off.  The circuit is completely passive and will work on dynamic and electret type microphones . . . Circuit by David A. Johnson P.E.-February 15, 2002

Remote Range Extender TV/VCR  -  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.   . . . Hobby Circuit designed by David Johnson P.E.-December 14, 2009

Remote TV Camera Power  -  A while back I received an email from a company with a problem.  They needed a security camera installed at some remote location.  The camera was a high quality color camera sending out standard NTSC video through a long 500 foot 50 ohm coax cable.  With some difficulty they got the coax strung.  They were told that there would be AC power near the camera location to power that device.  But, they then learned that in fact, there was no power available.  They thought about using a solar panel and a battery but they decided to call me for help instead.  Was there some way to power the camera without stringing another cable? . . . Hobby Circuit designed by David Johnson P.E.-July 03, 2011

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

Parametric Equaliser -  tailor your audio with this variable frequency cut/boost filter __ Contact: P. Townshend EduTek Ltd

Pardy Lights: an Intriguing Colour Display -  OK, so they're really "party" lights.  They're easy to build and produce random colour patterns to the bass beat from your music. __ SiliconChip

Part 1-IPod Super Dock Project -  This one goes out to everyone that has an iPod or two laying about and an itchy soldering iron and thinks that the standard USB or Firewire dock just isn't quite good enough.  The tiny thirty pin dock connector on the bottom of later model iPods contains quite a __ Designed by Will O'Brien

PCM2902 Soundcard with Microphone Input -  Many of us have a pair of headphones connected to the output of the computer sound card us either to enjoy songs, or a game.  Very likely your headphones and microphone, which also connect to the appropriate slot your sound card.

Peak program indicator, speaker powered -  This circuit requires no battery, being powered from the loudspeaker signal it is detecting.  When the voltage being delivered to the speaker exceeds the level set up by the preset RV, the LED indicator flashes. __ Designed by Richard Torrens

Peak Reading Audio Level Meter -  indicates peak audio response on an analogue meter, similar to a tape recorder recording level meter __ Designed by Andy Collison

Peak-reading meters -  This article first appeared in the April 1981 issue of Recording-engineer/producer magazine.   Peak reading meters, popular in Europe for years, are just now coming into greater favor in America, and for good reason.  The main purpose for having a VU meter is obviously to monitor signal levels going to a tape recorder, reverb unit, or some other level-sensitive device, to help optimize the signal to noise ratio of the audio sent to the device.  Too much level will produce distortion, and too little results in the inherent noise of the medium becoming a problem.  Unfortunately, a conventional VU meter responds to the average level of the program material and not to the peaks; yet it is these momentary bursts of higher level that become distorted first. __ Designed by Ethan Winer

Pedalboard Power Supply -  Pedalboard Power Supply with adjustable Old Battery settings __ Designed by Guitar Effect RC Keen

Pedalboard PS  -  Pedalboard Power Supply with adjustable Old Battery settings __ Designed by Guitar Effect RC Keen

Peppermill overdrive-A simple, transparent overdrive. Schematic & PCB/perfboard layouts. -  A simple, transparent overdrive. __ Contact: holler @ runoffgroove.Com

Perimeter Monitor -  Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area.  The cable can be buried in a hosepipe or duct and is concealed out of sight.  The mic is an ordinary dynamic mic insert __ Designed by Andy Collison

Personal Stereo Amplifier -  With the simple circuit, you can use your personal stereo to drive standard 8 ohm speakers.  

Phase 180 Plus -  An update/extension of the Phase 90 with extra stages and controls for the experimenter. __ Designed by Guitar Effect RC Keen

Phase 90/180 schematic -  The MXR Phase 90, plus extension to eight stages. __ Designed by Guitar Effect RC Keen

Phono Preamplifier -  Simple circuitry suitable for moving-magnet cartridges __ Designed by RED Free Circuit Designs

Phono Preamps for All -  Various circuits for moving coil and moving magnet pickups __ Designed by Rod Elliott  ESP

Phozer -  The original Phozer was a sound idea, but was hindered by its mashed-up development.  The circuit didn't really exceed the sum of its parts, namely Tim Escobedo's Idiot Wah and the LFO from the EA Tremolo.  The faux phase shifting effect was reasonably convincing at faster speeds, but the LFO failed to produce a true sweep at slower speeds.  Rather than ramp up and down, at slow speeds the LFO simply spent more time in the darker heel-down position between quick pulses of toe-down mode.  Also, we saw that using op-amps rather than discrete components would probably allow for a more complex effect with fewer parts. __ Contact: holler @ runoffgroove.Com

PICAXE Plays Music -  One of the most popular uses of PICAXE chips is in sound orientated projects.  Both the new PICAXE-14M and PICAXE-28X1 support the 08M 'play' and 'tune' commands, which allow the PICAXE chips to play mobile phone ring-tones directly via a piezo sounder. __ SiliconChip

PIC-Based Musical Tuning Aid -  This compact device will help you tune almost any musical instrumentacoustic or electronic.  It can produce any note on the tempered musical scale   (standard pitch) in any of the eight most commonly used octaves, with an accuracy of better than ?0.08% or 1.3 musical cents.  The selected note is compared with that from the instrument either by ear or visually by using an eight-LED stroboscopic beat indicator. __ SiliconChip

Pira CZ Compressor/Limiter/Clipper for FM Broadcasting -  Audio signals as music or speech have big dynamic ranges.  There are silent and loud sections.  These audio signals aren't too good for a transmitter, which requires audio signal with constant level on the input.  Limiter is a device, __   Jan Kolar

Plans for a Shotgun Microphone -  Also with Tube Lengths based on 1/4 Octave Frequencies. __ Designed by G.L. Chemelec

PL-CG (CTCSS) Filter Construction Projects -  Build several PL (CTCSS) Filters! 

Pop Free Microphone On/Off Switch Circuit -  This circuit uses a simple technique to eliminate the usual “pop” sound when an electret type microphone is switched on or off.  The circuit is completely passive and will work on dynamic and electret type microphones. . . Circuit by David A. Johnson P.E.-February, 2002

Portable Audio Amplifiers -  Above circuits are based on TEA2025 is a monolithic integrated audio amplifier in a 16-pin plastic dual in line package manufactured by UTC.  Circuit has an Internal Thermal Protector.  It is designed for portable cassette players and radios.  You can also use it as your PC Audio Amplifier. __ Designed by YMYA electronics-IZHAR FAREED

Portable CD Player Adapter for Car -  Whenever I'm in the car listening to my favourite CD, it always happens-my batteries go dead.  To solve that problem, I built this extremely simple regulator circuit.  It steps down the 12V from the lighter socket to 9V which is used by the CD player __ Designed by Aaron Cake

Portable Headphone Amplifier -  3V Battery powered High Performance unit __ Contact: Flavio Dellepiane, fladello @ tin.it

Portable Microphone Preamplifier -  This circuit is mainly intended to provide common home stereo amplifiers with a microphone input.  The battery supply is a good compromise: in this manner the input circuit is free from mains low frequency hum pick-up and connection to the amplifier is more simple, due to the absence of mains cable and power supply __ Contact: Flavio Dellepiane, fladello @ tin.it

Portable Mixer -  The target of this project was the design of a small portable mixer supplied by a 9V PP3 battery, keeping high quality performance.  The mixer is formed assembling three main modules __ Contact: Flavio Dellepiane, fladello @ tin.it

Portable Retro Hi-Fi Speaker -  Convert your speaker into a mini Hi-Fi system. __ Contact: Jameco Electronics

PortaPAL Public Address System-Part 2 -  Here's the good oil on putting it together and getting it to work.  We even describe an easy way to build a box. __ SiliconChip

Potpourri of Transistor Audio Amplifiers -  At a recent RASON meeting, I gave a presentation of how to design audio preamplifiers.  I thought it would be nice if we could now build some audio amplifiers to bring the output from these preamplifiers to levels which could drive a speaker.  I intentionally avoided the use of IC amplifiers to provide a real learning experience for audio amplifier design.  Although many IC amplifiers provide excellent performance at low cost, we need to learn the basics first.  I will address IC audio amplifiers in a future article. __ Designed by N1HFX

Power Amp with DIY Chassis -  This is a simple chassis using just 4 aluminum panels and 2 heatsinks.  Designed around dimensions to tightly pack in a LM3886 chip amp kit.  The top and bottom panels sit in ridges cut into the heatsinks with a table saw, and then the front and back panels just bolt into the end fins

Power Amplifier Clipping Indicator -  At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become "dirty".  If this happens too often or is too severe, tweeters are the first to gothey are damaged by the excessive power generated by a combination of "power compression" and the harmonics created when an amplifier clips.  The same may well happen to one's ears, but the effect is much more subtle (and cannot be fixed !). __ Designed by Rod Elliott  ESP

Power Audio Amplifier stereo with TDA7293-200 Watts RMS total-Includes Power Supply & PCB -  Amplifier circuit stereo audio with good power, using integrated circuit TDA7293 for up to 2x 100 Watts.  With Suggested PCB mounting design.  Includes power supply to the circuit itself, thus only requires a transformer to power.  PCB compact size even being single sided.  Allowing mount a power amplifier and compact with good quality, ideal for […] __ Designed by Antonio Rodrigues

Power Audio Amplifier with TDA7377 2.1-Stereo + Subwoofer 2x 12 Watts + 37 Watts -  Complete circuit power amplifier 2.1, 3 channel with TDa7377, include in the layout, power supply, bass filter as well as the full PCB layout.  Project amplifier ideal for various applications.  includes in the board, Power Supply, Preamplifier, bass filter, volume and tone control.     Eagle 3D view TDa7377 2.1 About designing amplifier with TDA7377 Stereo […] __ Designed by Antonio Rodrigues

Power Supply for a SE 300B Amp -  Schematic for the power supply __ Designed by Bob Danielak

Powerful Siren -  Simple circuitry No ICs 12V Battery operation __ Contact: Flavio Dellepiane, fladello @ tin.it

Powerful, 12V Mini Stereo Amplifier -  Getting lots of power from an amplifier when you only have 12V to play with __ SiliconChip

Practical MS Decoder -  The schematic diagram of the MS Decoder may look complicated but is actually quite simple.  Both the Mid and Side signals are initially. __ Designed by John Simonton

PreAmplifier Computer Microphone -  This circuit was submitted by Lazar Pancic from Yugoslavia.  The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs.  The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms.  Lazar has adapted the sound card to use a common electret microphone using this circuit __ Designed by Lazar Pancic from Yugoslavia

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