Hello,
Thanks George2, in the prospective of sending the unit to Spain for repair, I just opened it, its a mess of metal boards, circuits, and tested with it wide exposed and the noise was gone, somehow it was electric noise, some inside cable with bad connection or touching something it shoudn´t, but now is nice again.
My conclusion is: avoid this unit, is very badly constructed... despite the good preamps...
Thanks to you all.