This is a simple bridge amplifier based on TDA7240A. This circuit is designed for car audio system, but you may use this circuit for your small home audio application…
20W Bridge Amplifier using TDA7240A – [Link]
This project is a 20W audio amplifier based on LM1875 IC from National Semiconductors. With a 25V dual power supply LM1875 can deliver 20W of audio power into a 4 ohm speaker.
20W audio amplifier using LM1875 - [Link]
This circuit is a MOSFET Audio Amplifier rated at 25 Watt. It is high quality and simple design. There is also a kit available on the link below.
25 Watt MosFet Audio Amplifier - [Link]
This project shows how to build a Vacuum Tube Preamplifier based on ECC802S (12AU7 / ECC82) Vacuum Tube. This one is high voltage so it is geared towards more advanced builders. Follow construction details on the link below.
DIY Vacuum Tube Preamplifier Project - [Link]
Ruby is a battery-powered amplifier and it is an “enhanced” version of the Little Gem. This amplifier is based on LM386 chip and has an input buffer that is feeding the inverting input. The input buffer helps to retain treble detail going into the 386 chip. It is powered from a single 9V battery. Check schematic and construction details on the link below.
Ruby : A battery-powered amplifier – [Link]
The LM386 IC is a low voltage power amplifier. The gain is set to 20 but can be changed from 20 to 200 using external components. The basic setup is really simple using only a few components as shown on the schematic above.
Audio Power Amplifier using LM386 - [Link]
This project shows how to build an audio amplifier inside a Altoids tin box. The speaker, circuitry, AA battery and 3.5mm connector are fit inside the tin. Power is supplied by a Maxim MAX756 Step-Up DC-DC Converter and amplification is done with an LM386 op-amp chip. Follow instructions on the link below.
Altoids Tin Speaker – [Link]
This project is a small hand held device that allows you to create real-time noise loops with a metallic effect. It is using a microcontroller to create the noise loops and has three controls, tempo, sound and write. In the link below find instructions to build your own crazy looper. Schematics and source code is available. There is also the option to buy a kit.
Crazy Looper - [Link]
This project is an AVR spectrum analyzer based on Atmega8 AVR microcontroller an operational amplifier and a few other components. It uses HD44780 compatible LCD or VFD and supports following displays: 16×2, 20×2, 24×2, 20×4.
AVR acoustic spectrum analyzer - [Link]