6SN7 tube GTA vrs GTB


I would like to know the difference between the designation GTA and GTB.

Thanks
fordmod
OK. I've tried NOS RCA GTB's and never liked them. I am in Charlotte, NC. You?
That would be a little too far to drive. I'm in Indy! I thought perhaps I'd bring my tube collection over for you to try, before making any purchases. Here's a pair of the correct Sylvania VT231/6SN7GT tubes from a seller I've dealt with and trust very much: (http://cgi.ebay.com/Sylvania-6SN7GT-6SN7-VT-231-VT231-matched-NOS-pair_W0QQitemZ120282753596QQihZ002QQcategoryZ64629QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) Angie and Steve are in Australia, but get their tubes to you very quickly. If you can get those cheaply enough, and like them: The TungSol roundplates will REALLY make you happy! I'm saving a couple pair for when the TungSols and Sylvania 6SN7W's disappear altogether.
OK. I will check that out. Funny, I will be in Indy in two weeks for work....
Too bad you can't bring your system(and listening room) with you. Given so many variables- Tubes that sound perfectly natural in my system, could sound much less so in yours. I've a feeling you'll like the Sylvanias and TungSols though, and the VT-231 will be a less expensive foretaste.
how are the Sylvania 6SN7WGT that good? I was told they are GREAT. Is this true? The "best" 6sn7? How do they compare to the RCA GTB's?

Thanks,