Huh, I hear the laud boom sound always after windows starts.. but just ignoring it.. I have no Idea why it's happening. after it sound goes well till next restart So probably its different problem than yours.
AS I said I am using adaptive voltage in fact I am using more than 1.25V just set additional voltage to 1.25V in reallity it uses about 1.280V on idle and 1,312-1.328V(Not more) on heavy load/stress tests...
Check in The ASUS Z170 Thread, first post there is overclocking reviewScroll down till you see Screenshot with adaptive voltage settings, just try to put like 1.2 on additional voltage, or if you overcklocked try 1,25 or whatever you will need to ke...