Though I'm not a tube expert, I have bought tubes for my amps (a Mesa Boogie Blue Angel and a Marshall Bluesbreaker re-issue) from Mesa, Groove tubes and Fender at local guitar shops. After putting the tubes that I bought from The Tube Store into both my amps I can honestly say they both sound better than ever! The EH 12ax7eh tubes I put in the Blue Angel are far cleaner sounding than the Mesa or Groove tube 12ax7s Ive used in the past. I have had problems with microphonics and amp hiss with this amp and thought I was going to have to take it to a repair center, the new tubes make that trip unnecessary. The JJ el84s are also better sounding than the any of the past tubes Ive used. I had already replaced the 6v6s with EH 6v6eh tubes bought locally and the great sound they gave me with this amp prompted me to buy the rest from The Tube Store. As for my Bluesbreaker, I had already replaced the 12ax7s with some Mesas and wanted 6l6gcs to replace the Fender(Sovtek) 5881wxt tubes I was using. So I picked the SED 6L6GC tubes, biased them to 35ma and was blown away by the difference in sound these tubes made! I may try biasing a little higher if I can put my guitar down long enough to do it!