PiRetrocade Assembly Guide
Contributors:
LightningHawk
LightningHawk 
Audio Set Up
The simplest way to get audio for your arcade machine is to plug powered speakers into the audio jack. You can also change the settings in RetroPie. To use headphones, navigate to the RetroPie emulator and press A. Select Audio in the menu by pressing A again. Select option 2 to use headphones. select Option 3 to use HDMI. To get a portable solution-if you are making a cabinet, select option 4 and check out SparkFun's Audio amplifier kit. Just be sure to tie ground from the amp kit to a ground pin.