Hi videoracer,
Up until today my pre´s have yet to make any noise, they are very quiet.
You could be picking up some interference, sounds like a ground loop problem, try notching out with a filter plugin around 50/60 hz and see if it goes away, if so you have some kind of ground loop induced noise in your system.
It could also be your Behringer AD, (I don´t usually knock there gear as I use some pieces, BCF2000 and headphone amp

) but they do have a reputation for low quality control dfegad).