External USB audio, hiss and clicking sound

Hi

I didn’t see any passthrough option. It is set to 2.0 speakers.
I can’t find any asound.conf in the /etc/ directory. Am i supposed to create one from scratch? How?

Thank you for helping me :-).

Here is a screenshot of what I see in the menu:

This is the result of running “cat /proc/asound/cards”
1 [Audio ]: USB-Audio - NAD USB Audio
NAD Electronics NAD USB Audio at usb-bcm2708_usb-1.4, full speed

This is a link to the data sheet of the DAC:
http://nadelectronics.com/download.php?131209102650-NAD_MDC_DAC_2-0_DataSheet.pdf|MDC%20DAC%202.0%20USB%20Digital-to-Analogue%20Converter

Regards