Lightning is a purely digital interface (unlike USB-C which does have the capability to output analog audio directly and is replacing Lighting on new products). So the Lighting connector on the EarPods will need to contain:
- A DAC to convert the interface to analog audio in order to drive the speakers inside
- An identification chip of some sort to tell the host device what's been plugged into it and what its capabilities are
- An amplifier circuit powerful enough to drive the in-ear speakers
For reasons of size, these functions will most likely be combined into a single physical chip.
What travels down the cable from the connector to the in-ear parts will be analog audio - indeed, the alternative version of the EarPods has a 3.5mm stereo jack plug for use with any audio device that has a headphone socket.
The Lighting interface also has power pins that supply the interface circuits in the EarPod connector.
So to achieve your aim of connecting a set of EarPods with a Lightning connector to a 3.5mm analog output on some other piece of equipment, you would need the following:
- ADC converter to digitise the audio
- Processor to control the ADC
- Lighting interface port of some sort to plug the EarPods into
- Software to run the whole thing
- Power supply
Is it doable? Yes, given enough knowledge and time. Is it cheaper than buying a set of EarPods with a 3.5mm plug? No. Is anyone ever likely to make such a thing? Probably not as the previous answer shows there would likely be little demand. Can you do it with a passive adaptor? No, as you have to carry out conversion of analog signals into digital signals.