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 do I connect the circuit 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.

To connect the circuit together and determine what parts to use, you can follow these steps:

1. Start by understanding the requirements of each component in the system:
- Accept a standard headphone audio jack as an input: You will need a connector that can interface with the audio jack of your portable audio device.
- Built-in speaker: You will need a speaker that meets the required specifications.
- Volume control: A potentiometer (variable resistor) can be used to adjust the volume continuously.
- Treble or bass control: Active filters can be used to control the desired frequency range.
- Power supply: Determine whether you will be using batteries or an external DC power supply.

2. Design the active low-pass filter, active high-pass filter, and band-bass filter:
- Choose appropriate opamps, resistors, and capacitors for each filter based on the desired cutoff frequencies and component values.
- For the low-pass filter, select components that allow frequencies below 300 Hz to pass through.
- For the high-pass filter, select components that allow frequencies above 900 Hz to pass through.
- For the band-pass filter, choose components that allow a specific frequency range between 300 Hz and 900 Hz to pass through.
- Connect the input and output terminals of each filter accordingly.

3. Design the volume control circuit:
- Choose a potentiometer with the desired resistance value.
- Connect the potentiometer in series with the audio signal, allowing the resistance to control the volume level.

4. Design the power supply and amplifier section:
- Select appropriate operational amplifiers and power amplifiers based on the power requirements of your speaker.
- Connect the input of the amplifier to the output of the filters.
- Power the amplifier using the chosen power supply method (batteries or DC power supply).

5. Implement additional features if desired:
- If you want to add a notch filter to attenuate any unwanted frequency (e.g., 60 Hz hum from power lines), design and integrate this into the circuit using appropriate components.
- You can also add other features like indicators, packaging, stereo sound, equalizer, etc., based on your requirements and available resources.

It is important to note that the choice of components and circuit design may vary depending on the specific requirements and constraints of your project. It is recommended to consult resources such as datasheets for components and reference designs to ensure proper functionality and performance of your speaker system.