100ma would make the tubes last forever but it would sound like doo doo. They might set it that way when it's under warranty, just to make sure the tubes won't wear out. Well yes eurotubes is correct at 180 ma. With 180 reading, the actual plate current is around 40 ma per tube or 160ma plate all 4 tubes. The other 20 ma is being used by preamp tubes, screen grids, and slight leakage of filter caps etc.