I think Kal may be on to something. To get "full signal", you would want to have the Freya+ in "passive mode" and turned up all the way. That would be full signal pass-through. If you have the Freya+ in tube gain mode, you'll be adding 12db of gain and I can believe you could get some noise.
Try it in passive mode, if you haven't already". Just remember, re-do your HT setup with the Freya_ in passive mode, volume control all the way up.