Instructions

Question

The goal of this project is to design, simulate, build and test a simple speaker system that can connect to a portable audio device such as an mp3 player or laptop. The system has the following requirements:

§ Accept a standard head-phone audio jack as an input.

§ At least one built-in speaker.

§ It must provide a means of controlling the volume continuously.

§ It must also have a means of controlling the treble (frequencies > 900 Hz) or the bass (frequencies < 300 Hz).

Only simple components such as switches, potentiometers, LEDs, operational amplifiers, power amplifiers, resistors, capacitors and inductors are allowed. It may be powered by batteries or an external DC power supply (bench supply or DC converter), but it cannot connect directly to a wall socket (120 V AC). You are welcome to add additional features such as packaging, an on/off switch, indicators, both bass and treble control, 60 Hz notch filter, printed circuit board, stereo sound, an equalizer or anything else you may think of, but none of these features is required.

I know that I need to have a active low-pass filter, active high pass filter, a band-bass filter and a notch filter...how do I connect the circuit together..how to decide what parts to use..Help any designers..thanks..

What you ask is what you are to figue out.

Why do the fiters have to be active? And why a notch filter?

You need to work from input level/impedance to output level/impedance. All the components listed will do. The simplest way will be use opamps, with rc filters configured low and high.