The 3.5mm auxiliary input jack connects directly to the PCB. On the schematic, you will see the Left and Right signal traces running from the jack. These traces often pass through coupling capacitors (usually small electrolytic or ceramic caps, around 1µF to 10µF) to block any DC offset from the source device while letting the AC audio signal pass.
Before diving into the specific traces of a circuit diagram, it is crucial to understand what the diagram represents. The Creative A220 is a 2.1 channel system. This means it consists of two satellite speakers (Left and Right) handling mid-to-high frequencies, and a subwoofer unit handling low frequencies. creative a220 circuit diagram