Скачать или смотреть HELP WANTED!! Weird buzzing noise on StudioProjects VTB1 !!please read the description!!

Symptoms:

First five to 15 minutes of use, VTB1 works as it should
After that, this helicopter-like buzzing noise begins
Usually it is constant (like in the end of this video)

Signal chain:
-Mic (T.bone SCT800 and Röde NT2-A (Both tested) )
-VTB1 unit
-insert to "t.c. electronic Triple C"compressor
-output to M-audio profire 2626

How I pinpointed the problem into VTB1 (Did I miss something.?):
-Connected mic(s) straight into M-audio, no problem
-Disconnected inserted HW
-Shutting down the VTB1, the buzzing stopped

Other things to mention:
-tube blend is positioned to Solid state or at full tube (no effect)
-48volt phantom is on or off (no effect)
-Resistance switch behind the unit is in position of 50 Ohms or 200 Ohms (no effect)
-High pass filter on or off (no effect)

Also tried changing the tube to a new one, no help.