The University of Southampton

# A-Level Physics Music Mixer Kit

This initiative has been supported by the UK Electronics Skills Foundation (UKESF)Institution of Engineering and Technology (IET)

The Music Mixer circuit board incorporates core electronics concepts suitable for A-level Physics students.

The circuit combines two audio signals, for example music from mobile phones, enabling users to control the volume by experimenting with different electronic components, learn about electronic sensors (e.g. LDRs) and resistor dividers.

The design aims to expose all components and demystifies electronics for students.

The board also has dedicated sections for determining Planck’s constant – by measuring and plotting the voltage and current through four differently coloured LEDs – and experimenting with capacitor discharge.

The board is split into three dedicated sections: Music Mixer, Capacitor Discharge, and Planck’s Constant.

### Music Mixer Section

This introduces potential dividers using an audio mixer circuit. The board has two audio input channels that are mixed together using an amplifier. The volumes of the two channels are controlled by potential dividers where the resistor values can be changed or exchanged with LDRs, or other resistive elements, to control the level of each channel.

## Video Tutorial

This tutorial video walks viewers through the typical use of the Music Mixer and the experiment described in the accompanying exercise notes.

### Capacitor Discharge Section

This allows students to explore the discharging of series and parallel capacitors through different resistances. Jumpers J1 and J2 allow the capacitors to be connected in series or parallel.

## Video Tutorial

This tutorial video walks viewers through the typical use of the Capacitor Discharge Section part of the kit, and the experiment described in the accompanying exercise notes.

### Planck’s Constant Section

This allows students to estimate Planck’s Constant by measuring the voltage and current characteristics of a range of different colour light emitting diodes (LEDs). A spreadsheet is provided for students to enter measured values, and estimate Planck’s Constant.

## Video Tutorial

This tutorial video walks viewers through the typical use of the Planck’s Constant part of the kit, and the experiment described in the accompanying exercise notes.

The videos below enable you to find out more about the Music Mixer kit, and the electronic engineering principles that make it work.

## Potential Dividers

This video explores the potential dividers on the Music Mixer kit, how they are used to mix the two input channels, and the wider applications of this technology.

## Operational Amplifiers

This video explores the functionality of an operational amplifier, how it is used in the Music Mixer kit, and some of the other uses of this widely used electronic component.

### Troubleshooting

If the Music Mixer does not work, first of all:

• Check the power is switched on; the power LED will be lit. If the power LED does not light, replace battery (rechargeable batteries are fine) and remove all wires from board. Ensure you do not directly connect “V” to “GND”.
• LED1-4 will only light when an ammeter is connected between TP6 and TP7 and a jumper is connected above the LED.
• Check that the audio inputs and output jacks are firmly seated.