Welcome to Sound Design.
The three audio input jacks on the subwoofer are each two channel 3.5 mm TRS (tip-ring-sleeve) connections colour-coded according to the PC 99 standard:
Lime Green - Front left and right
Black - Rear left and right
Orange - centre and subwoofer (both mono)
The subwoofer channel is known as LFE (low frequency effects) in the Dell ...
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 ...