Please help

Hello I am new to this and hoping i can get some help. 

I ordered the Drop + EPOS PC38X headset and I am having trouble connecting it to my pc. When i first plugged them in directly to my pc  they were not loud enough so I bought what I thought was a DAC (Douk U3), well it turns out this is only a amp. I hooked everything up and although they were much louder they had a horrible hissing sound and of course my mic no longer works because I am just using a single 3.5 mm headphone jack to RCA cable to the amp. 

I think the hissing is due to the headset cable and adapter not working so I may get a new output cable as well. (background noise changes/diminishes when i wiggle to cable and 6.5 mm adapter. 

Is it possible to get a mic and audio input (pink and green) to RCA cable so my mic will work? Please help I am so lost!