My suggestion to you is DO NOT buy any new tubes till you get the buzzing issue resolved. If you cannot get the buzzing issue resolved, as previously suggested, purchase a new amp.( life is to short to listen to a buzzing system) When you get to the point that you are ready to purchase new tubes DO NOT buy them from outlets like ebay or amazon, those sellers are far from professional tube dealers. A professional tube dealer will perform several different tests and use different pieces of test equipment for those tests before their tubes are determined to be good enough for sale. There is a lot of dishonesty in the tube business, many of our customers paid high prices for what were supposed to be NOS (NEW old stock) tubes but after the tubes were tested by a professional the tubes were determined to be USO (USED old stock) or even worse JOS (JUNK old stock) Most non professionals only run one test on there tube tester and that only determiners whether the tube is good or bad and what percentage of life is left in the tube. All NOS tubes should test at 100% and nothing else or it is used. If you are a critical listener and have a very reveling system, even with tubes that test 100%, only a certain percentage of those tubes test good enough for preamps and even a smaller percentage for phono preamps. Another trick we have seen, that tube buyers must be aware of is this, sellers are buying cheap tubes and using steel wool to remove the name off of the tube and then painting a different name (one that is much more expensive) on the tube and of course that tube tests out at 100% so it is sold as NOS. Most of the time if you put these tubes in the freezer over night you will be able to see parts of the printing that was removed. Buy from a reputable tube dealer and avoid all these problems and more.
