Now I'm sure a lot of pepole will strongly disagree, but do your wallet a favor and try the JJ's or Sovteks before dropping a bunch on used Mullards. I have no problems with them. So the tube tester says it tested as such, big deal. I've fried a few in my day and the testers still said they were OK. They just couldn't handle a full load. If you have to compare sonic differences borrow a Mullard off a friend. The JJ's are on sale at AES and a few bucks cheaper than Uncle Ned. But I still buy all my audio tubes off him regardless.