Tested with the latest Android and Ubuntu OS for XU4, C2 and C1+. You don't need any soldering. It is ready to go.
If you have old version of OS, update it to the latest version first.
This uses I2S as digital sound standard for audio output. It is super easy. You'll be rockin' out in 15 minutes. step1. Plug 2 x 2 Watt 4 ohm stereo speakers to the connector on the Boom Bonnet board and attach them with sticky glue. step2. Connect the GPIO ribbon cable one side to the boom bonnet board and the other side to ODROID board. step3. Update the OS to the latest version.
You can easily adjust the audio output level with a potentiometer on the board.