Me, if I ordered and paid for a Sylvania 5751 triple Mica tubes, I should get a Sylvania 5751 triple Mica tubes, period!
I do not need someone telling me that the RCA is better sounding than the Sylvania etc. etc. The bottom line is, you should get what you paid for. What if the Sylvania sounds better to you than the GE or the RCA? Only you can tell in your system.
Oh, the label(1 and 2) is the Gm measurements of the tube where (first one indicates triode 1 and the second triode 2 for the 5751 which is dual triodes) which, in most instances, many confuse as an indication of the tubes being the numbers to match so that the tube pair can be called "match pairs".
I do not need someone telling me that the RCA is better sounding than the Sylvania etc. etc. The bottom line is, you should get what you paid for. What if the Sylvania sounds better to you than the GE or the RCA? Only you can tell in your system.
Oh, the label(1 and 2) is the Gm measurements of the tube where (first one indicates triode 1 and the second triode 2 for the 5751 which is dual triodes) which, in most instances, many confuse as an indication of the tubes being the numbers to match so that the tube pair can be called "match pairs".