Can I just connect the headphone to the 3.5mm adapter and then to the
If I do so, will the sound quality decline?
Or it might damage the devices?
A little more on sound quality. Headphones comes in various types and for various purposes. USB adapters comes in various types as well. Some headphones require a bit more power than you can get from the typical USB adapter and some are quite happy. So go ahead, you will not hurt anything. If you find the sound level to be too low for your happiness, you will need either a different headphone or a different USB adapter.
- as for headphones, typically you will wish for a low impedans version (not the 300 Ohm version).