Quantity   Component name
1 × Raspberry Pi 3 Model B+ Should work on any Raspberry Pi
2 × VU Meters Any analog VU Meter will do, ideally salvaged from old hifi equipment. Technically you can also use a voltmeter that is rated for 0 - 5V.
3 × Trimpots You should be able to adjust resistance between 0 and 20k Ohms. Maybe use more trimpots to get a finer adjustment range
1 × Multimeter
1 × Bench Power Supply ideally can support low voltages of less than 3 V. Best: can step up in 10mv increments
1 × Wires You always need wires
1 × Optional: MCP4922 DAC 2 Channel, 12 bit, Digital to Analog Converter
1 × Optional: MCP4725 DAC 1 Channel, 12 bit, Digital to Analog Converter
2 × Optional: Capacitors 10µF and 100nF Capacitors