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 that can be varied in number and/or disposition to suit everyone needs. The three main modules are: Input Amplifier Module: a low noise circuit equipped with a variable voltage-gain (10 - 100) preset, primarily intended as high quality microphone input, also suitable for low-level line input. Tone Control Module: a three-band (Bass, Middle, Treble) tone control circuit providing unity-gain when its controls are set to flat frequency response. It can be inserted after one or more Input Amplifier Modules and/or after the Main Mixer Amplifiers. Main Mixer Amplifier Module: a stereo circuit incorporating two virtual-earth mixers and showing the connection of one Main Fader and one Pan-Pot. The image below shows a Block diagram of the entire mixer featuring four Input Amplifier Modules followed by four in-out...