This project shows how to build a parabolic microphone.
Employing any curved reflector and a microphone will greatly enhance the long distance performance over using the microphone alone. Although the reflector used in this particular project was not truly parabolic, it worked very well.
Parabolic Microphone - [Link]
This project is an amplifier designed to drive an 8 ohm speaker or phones to an extremely loud level at small input signal down to 700uV RMS. Although designed to be used with the parabolic microphone also listed on this site, this amplifier is also very well suited for use with any Crystal Set or other low signal output device.
Very High Gain Audio Amplifier – [Link]
This project is a LED lighting system that is able to pulse with the music bit. It is based on Arduino and a PC for signal processing. The audio output is fed to the PC and a script is making the process and calculates the light levels which then are send to Arduino. Arduino is controlling the LEDs via a control board. The system has four LED modules that each have two 4-channel LEDs (red, green, blue, white), this means that is required 32 PWM signals to control all the LEDs. To achieve that the author used 2x TLC5940 16-channel PWM chips. These ICs act like cascading shift registers. Check details on the link below. [via]
Audio controlled LED party lights - [Link]
This project is a VU meter using 14 IN-13 bar-graph Nixie tubes. The producing effect is really nice. Each of the tube is connected on driving circuitry that include bandpass filters of 60, 150, 400, 1000, 2500, 6000 and 15000kHz pass. Then each filter output is converted to DC and converted from logarithmic to linear scale suitable for Nixie tubes.
Nixie VU meter - [Link]
This project created by Paul Bishop is a real time spectrum analyzer based on Arduino platform. The output is displayed on TV output. . He used an FFT library by Arduino forum user deif to convert an audio input into frequency data, and the TV out library to display the results. [via]
Real-time spectrum analyzer powered by Arduino - [Link]
This circuit is a simple intercom circuit based on LM386 low voltage audio amplifier. It uses 8 ohm speakers that works as a microphone and as speaker at the same time. A 10k potentiometer is used to adjust the volume. It also has a double pole double throw switch that is used as push to talk switch.
Simple two way intercom – [Link]
This project is a 2x2W Audio Amplifier based on LA418. This amplifier is very easy to build because it has not complicated parts and will cost around 4$. Check schematic and PCB on the link below.
LA4182 Audio Amplifier 2×2 Watts - [Link]
Halloween is always a great opportunity for hackers to take their creative projects to the streets. This year at NerdKits, our Halloween costume is the Human Theremin. The costume features two homebuilt infrared distance sensors mounted on the wrists. Someone wishing to “play” your costume can move his or her hands up and down above the distance sensors. One hand controls the pitch of the note, and the other controls the volume.
All said, we hope our costume is a big hit at Halloween parties, particularly because it allows others to interact with the costume (and can be really loud!). As always, we cover in-depth the concepts behind the electronics and code that we publish. This video can be a great introduction to phototransistors, triangle waves, fixed point math, and more, to help you learn and extend these techniques to your own projects. Happy Halloween!
Human Theremin Halloween Costume – [Link]
Rudolf Moers from the Netherlands has kindly sent us details of his parallel push-pull 300B monoblock tube amplifiers to share with the DIY Audio community. It should be quite obvious from the photographs that the design and construction of a pair of amplifiers this size is by no means a small undertaking. Rudolf tells us that he spent about 14 months designing and constructing the pair of monoblock amplifiers. The total cost of each amplifiers was about 1300 Euro, or about $1760US as of 29 September 2010. Each monoblock weighs 25 kg (55 pounds) and the overall dimensions are 530 mm deep, 390 mm high, 400 mm wide.
Parallel Push-Pull 300B Tube Amplifiers - [Link]