External usb hda standby

Hi ,just a dumb question:
When I star Roon, my usb hda start to run and even I play nothing it runs all the time.
If in setting I select disabled and then enable it works like it should be:standby
Library available and i can play a song ,then it goes in standby mode.
How to make this setting from the beginning ? Starting in standby mode ?
Tks Giovanni.

Any help?
Tks Giovanni.