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!

If you want big bottle STR sound this is as close as it gets!

If you happened to grow up in the 1970s and you were lucky enough to have an uncle with a music store you KNOW what vintage amps sound like. These tubes are the best bet for getting the CBS Fender tone. Clarity and headroom are as almost good as the original STR 387s, and fall just a tad shorter than the STR 415s. Great for hi fi too! Chiming rich highs, warm bright mids, and a tight low end. Detail is the best of all the modern 6L6GCs. They can be a bit microphonic in combo amps. This is not very common, and not usually to any great extent to the point of being too objectionable. This is another of my favorite 6L6GCs. Very low rate of failure, especially compared to JJ. The only thing better is real NOS big bottle Sylvanias.

As close to an STR 387 as you are gonna get now.

I finally had to retube some of my old Fender amps from the 1970s. These were as close to the STR-387 as I could find. The Svetlana New Sensor is similar but the highs are a bit airy and flutey compared to these. These have that chiming bell like tone. Nothing will replace the STRs or non STR big bottle Sylvanias, but these are pretty close. Get a lower number for the non STR387 or 415 sound which I really like a lot too. Those are not as clean, and just sound great. These are a close second and don't cost $100 each.