The tube certainly could be the problem, Oliver. However, I would suspect that the re-orientation in the room has more to do with it. I rotated our system from one wall to another, and I would have thought that we'd changed at least one of the components. Also, each time you have listened since returning, the amp has had 25 minutes or so to warm up, correct? And you're using all the same cords/cabling as before?
Hope all is well with you,
Howard
Hope all is well with you,
Howard