Besides some neat symbols for where the screws go the mainboard carries these chips:

ATS2825 Bluetooth Audio Solution from Actions Technology

NTP7513 audio amplifier

AH1834 IC

The two 72015 S0180 JRC are most likely audio amplifiers from the company New Japan Radio.

On the rear side of the board we find three line-in jacks labelled "AUX IN", AUX OUT" and SUB OUT", a button, an LED, and some additional chips:

CHIPSTAR CS5026E Audio Amplifier

And again the CN3704 Standalone Li-ion Battery Charger