An app note from Atmel, digital sound recorder with AVR and DataFlash (PDF!):
This application note describes how to record, store and play back sound using any AVR microcontroller with A/D converter, the AT45DB161B DataFlash memory and a few extra components.
This application note shows in detail the usage of the A/D Converter for sound recording, the Serial Peripheral Interface – SPI – for accessing the external DataFlash memory and the Pulse Width Modulation – PWM – for playback. Typical applications that would require one or more of these blocks are temperature loggers, telephone answering machines, or digital voice recorders.
Digital sound recorder with AVR and DataFlash - [Link]
by MrLeeh @ instructables.com:
I wanted to have my personal, nice looking Mediabox with a big display and remote control. I’ ve been playing around with the Raspberry for a while so I decided this would be the platform of choice for this project. I’ m actually a fan of Steampunk so I decided to use a Steampunkish style for the box.
Raspberry Mediabox Steampunk style - [Link]
5W Stereo Audio Amplifier project based on BA5406 IC which is suitable for application like stereo radio cassette player, stereo components systems etc.
The Heart of the project, BA5406 is a dual OTL monolithic power IC with two built-in, high output speaker amplifier circuits. High output of 5W×2 can be produced when VCC=12 V and RL=3Ω, and 2.8 W×2 when VCC=9V and RL=3Ω. The BA5406, which uses a high allowable power dissipation package, has a simple heat-sink design.
5W Stereo Audio Amplifier - [Link]
Focus a beam of sound at objects or into your head!
The Soundlazer directional audio project is the continuation of my first and very successful project here on Kickstarter. I developed the Soundlazer “Snap” during my quest to lower the cost of this amazing technology and give backers the opportunity to explore new possibilities in directional audio.
Parametric speakers like the Soundlazer are directional speaker systems. They use ultrasonic carrier waves to transmit audio to listeners in a focused beam of sound that acts like light from a laser. Generally speaking, only the person standing in front of a parametric speaker can hear the audio being transmitted. People to the sides of the directional audio source hear little or no sound.
Soundlazer “Snap” – The Directional Parametric Speaker - [Link]
This project is designed to operate with minimum of external components. This amplifier offers high quality and high performance audio at very low distortion. Project is based on nationals LM1875 IC. The IC is thermal and short circuit protected.
The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications, the project work on single supply. Device overload protection consists of both internal current limit and thermal shutdown.
20W Audio Amplifier - [Link]
We are building another enjoyable weekend DIY project. This is an audio power amplifier based on LM1876 which can deliver up to 20W per channel into 4 or 8 ohm load and guarantees less than 0.1% THD + N (Total Harmonic Distortion + Noise).
The amplifier is powered by -15 0 15 VAC symmetrical supply. The full bridge diode rectifier and the smoothing capacitors convert the AC input to ±21 VDC which is used to power LM1876. The inductors on the AC input line reduces the noise arising from the mains line.
DIY LM1876 Dual 20W Audio Power Amplifier - [Link]
This article introduces high quality digitally controlled 2.1 channel analog audio power amplifier system. This project is mainly based on TDA7377 AF power amplifier and PIC18F452 8bit microcontroller. Basic technical features of this receiver are covered in table1.
This unit is specifically design to work with PC sound cards, radio receivers and CD/DVD/Blue-Ray players.
Digitally Controlled 2.1 Channel Analog Audio Power Amplifier - [Link]
Voice Module 60 Sec project will playback and record up to 60 seconds of voice message. This circuit is an excellent choice to add voice to your project.
60 seconds Voice Record – Playback module - [Link]
This project is intendant for use as low frequency class AB audio amplifier.
Project is built around TDA2006 PENTAWATT package. TDA2006 provide high output current and has very low harmonic cross-over distortion. Further the device incorporates an original (and patented) short circuit protection system comprising an arrangement for automatically limiting the dissipated power so as to keep the working point of the output transistors within their safe operating area. A conventional thermal shutdown system is also included. The TDA2006 is pin to pin equivalent to the TDA2030.
12W Audio Amplifier - [Link]
This project is a message recording board capable of recording 120 secs of audio. This project is designed around ISD25120 which can store 120 Seconds audio. Recording and playback operations are controlled with tact switches. The kit has an onboard microphone and LED to indicate the functions of Play and Recording. IC has a re recordable non-volatile memory which means that the message will be stored even after the units are turned off and even when it is turned on again.
120 Seconds Voice Record – Play Back - [Link]