I tried to play some wav files with Java (javax.sound.sampled) on my Beagleboard. It worked without Exceptions but I didn't hear the sound. The hardware was not the problem...

By default, sound output was set to muted

I solved the problem with

Use alsamixer for the configuration:

Alsamixer

Set Headset volumne Toggle mute for HeadsetL Mixer AudioL1 and HeadsetR Mixer Audio R1 (Press m key) Check volume for DAC2 Analog

Test: