I’ve got the 7U 104HP performance case. Currently on my 1U row, I am using Quadratt 1U as my main mixer alongside the 1U headphone. Yesterday, I started to notice quite a strong hissing when nothing is plugged and starting with knob is at 1/3 volume. Now, I’m also starting to hear that hissing on top my audio as-well, especially when just playing drums with a lot of blank audio portion and it starts to get really annoying as I can’t not hear the hissing anymore, and I guess before I was just not paying attention. Any idea why I’m having this issue; is that normal ?