Not sure if you're trolling, you've been told a number of times the APM are active headphones only. You will hear nothing if the battery is dead. The only input is a USB-C input that will accept a digital signal.
At a minimum, you need to have an onboard DAC and headphone amp to convert the digital signal to analog to be sent to the speakers. That requires power.
In the case that you're using the USB-C to 3.5mm cable to listen to some devices 3.5mm output, the APM will need to power it's internal DAC and amp, in addition to, being in USB host mode and sending power to the USB-C to 3.5mm cable to power the ADC in the cable.
