I experienced the same thing when I first switched power tubes in my Jolida a while back...new KT120s. Freaked me out but it stopped, so I can only assume the tubes have some external coating or an adhesive on the tube base or something, as it happened again when I stuck a new pair of 88s in the thing. I now simply call it the "new tube smell." It went away after the tubes were in use for a day or 2 and never came back. I bias according to the amp specs, not the tube type recommendations and that seems to work for my amp as it sounds fine and the 120s are holding up well.