MacaronKit: USB-Powered Mono Audio Amplifier

In this Instructable, you'll make a USB-powered amplifier for an audio speaker. This is designed to work with haptic feedback for online tools like Macaron (http://hapticdesign.github.io/macaron) and VibViz (http://www.cs.ubc.ca/~seifi/VibViz/main.html), but you can use it with any type of speaker you want to amplify.

The unit takes power from a computer's USB power to amplify the computer's audio output. This Instructable covers mono amplification only. It should be adaptable for stereo, but you'll need to get stereo audio jacks and a stereo amplifier. Also note that in the picture the USB jack has a longer wire; we recommend having a shorter USB wire, and a longer male audio jack. The goal is to have the unit plug into both the USB port and audio jack of most laptops or computers, so cut the lengths appropriately for your computer.

To build this Instructable, you will need the following materials:

• 1x PAM 8302 mono class-D amplifier
  • Digikey: 1528-1492-ND
  • https://www.adafruit.com/product/2130
• 1x 3.5mm jack (f)
  • Digikey: CP-3506-ND
• 1x 3.5mm jack (m)
  • Digikey: CP3-1005-ND
• 1x USB Type-A male plug
  • Digikey: 1528-1179-ND
• 1x Project box
  • It must fit the amplifier. We use HM907-ND with L 50mm x W 35mm x H 15mm.
• ~40cm stranded wire x2: ground plus signal; we use red/black ribbon

• solder

You'll also need access to the following equipment:

• a soldering iron with a narrow tip
• a vice
• a rotary tool, drill press, or other means of cutting holes in plastic

Be sure to connect the ground wire (in these images, the black wire) to the ground in the audio jack (the longer part). Do this for both the male and female jacks. I recommend keeping the female wire shorter (~10cm), but making the male plug wire a bit longer (~20cm).

For the USB wire, make sure to get the ground and power right - look at the picture to double check. We recommend keeping this short (~10cm).

Look closely at the amplifier terminals to make sure you connect the wires the right way:

• The USB wires should go in the 5V power and corresponding jack. This will power the amplifier from the computer's USB ports.
• The male audio jack should go to the audio input, next to the USB; this will receive the audio signal from the computer.
• The female audio jack should go to the load terminals at the other end of the amplifier. This is where you can plug a speaker or voice coil.

First, place the amplifier in the box and mark where the wires will exit the box. Use a rotary tool to grind a 1-2cm semi-circular hole for the wires. High speeds will grind faster, while low speeds can help smooth the hole. Do this for all three wire holes.

Screw the project box lid and test it with your computer. You're done!

If the lid can't quite close, you'll want to make bigger holes in the project box. You may also want to check the wiring with a multimeter to make sure everything is connected.