Why Power Tubes Arc
Tube arcing is not necessarily a result of a "bad" tube or a "bad" design. It is far more likely the result of using the tube longer than you should for the application you’re using it. This interesting article, published in audioXpress, November 2004, remains a great read. At the time it also originated a response from Eric Barbour and Ed. T. Dell regarding their experience with cathode stripping.