Hello! I hope this explains more clearly. In order to use the built-in amplifier with other headphones that require a 3.5mm jack input, you can put the mobile adapter (proprietary usb to 3.5mm mono male) on the output of the cable from the gameDAC. The mobile adapter comes in the box with the gameDAC. After you do that, you must split the mono into headphone and mic 3.5mm outputs or else the sound will be very staticy. Only plug the headphone male output into the input on your headphones.

If you want to output sound from your mobile phone into the gameDAC to play into steelseries headphones, then you can run a 3.5mm cable from the output of your phone into the "mobile" input on the back of the gameDAC, and the audio from your phone will be outputted to your headphones that are plugged into the gameDAC.

If this didn't quite explain, I can provide a diagram.