So my TD started snapping and cracking wierd screeches... First thought was wiring as I had installed A variable NFB a couple years ago. So I pulled it out and returned the amp to original. And still had the problem... Ended up being one of my 6V6 power tubes. Had a spare so it's all good... Got a new matched pair coming so will have a spare JJ when they get here. Im actually glad to have it back to original.... Sounds fantastic!