6SN7 tubes


Come looking for a little help. I have a Mastersound Compact 845 amplifier, and I'd like to put some NOS tubes in it to replace the stock Electro Harmonix. Not the power tubes, just the driver and pre-driver tubes. Kinda stuck with Shuguang for the power tubes...

Anyways, the pre-driver tubes are 12AU7/ECC82's, and the driver tubes are 6SN7's. Problem is, the pre-driver stock tubes are labelled 12AU7A...the driver tubes are labelled 6SN7GTB.

I have a matched pair of NOS Telefunken ECC82/12AU7's- minus the "A" designation at the end. Can I drop these in, or is it a question for the maufacturer? Also, I'm hunting for some NOS 6SN7's- does it matter if they're straight 6SN7's, 6SN7GTA or GTB?

What's the difference with these minute designations at the end of the tube name? Am I overcomplicating things here?

Thanks in advance for any advice!
When in doubt you should check with the Manufacturer before making any changes.That said.
If your driver tubes are 6SN7GTB you can NOT use the 6SN7 or substitutes other then 6SN7GTA
The GTB and GTA tubes have higher voltages that your amp requires.
Your Telefunken's can be used.
You also may want to look into some Shuguang 845B tubes
Much better then the Shuguang standard 845.
Some further 6sn7 family info: (http://home.att.net/~chimeraone/6sn7sound.html) That your equipment has those higher voltage tubes installed, does not necessarily indicate that the piece is operating at higher voltages. DO contact the builder, and inquire. There are a number of NOS tubes that WILL increase your listening enjoyment, IF they can be utilized.
Here is an interesting piece on the 6sn7..... http://www.6sn7.com/
Thanks, everyone. Much appreciated. Goldeneraguy, a pair of 845B tubes is in the works already.
AFC, the 845 output tubes require a very high drive voltage (more than 200V peak-to-peak), in order to reach full power, therefore I assume that your amp must use 6sn7GTA or GTB, which can be operated at higher plate voltages.
Older 6SN7 tubes will work maybe for a month or two, then fail.

The 12au7 A suffix means controlled warm-up time, essential in series-connected TV heater circuits, not important in audio amps.
You will notice that the Telefunken Ecc82 tubes and most european 9 pin tubes flash when turned on. That is a sign of non-controlled warm-up...let's call it normal warm-up. No harm done, just enjoy the music.
If the Tele tubes sound a little bright in your system, Ecc82 tubes made by Philllips Holland, Amperex or Valvo do sound more "musical".

My preferences in terms of NOS 6SN7s are Sylvania brown base JAN-6SN7WA and the various Tung-Sol black plate versions. RCA GTA tubes are fine tubes too. I find the red base 5692 military tubes over-rated.
Because you are shooting for the best, I suggest that you bypass ECG Sylvania / Phillips ECG or GE 6SN7s, those tubes are well made and reliable, though not top audio performers.

Also avoid any late-production button-base 6SN7s. By the time those tubes were manufactured, the metal stampers were worn out and those tubes had become generic replacement/repair parts for old TVs.
good luck
Thanks, Casouza! Went with RCA JAN VT-231 tubes, the ones with grey glass. They're a little darker sounding, and are a good match.
You should try the Sylvania VT231's.
6sn7 should be properly matched with balanced triode-triode and tube-tube,not more than 10% with their transconductance and plate current.
The shuguang 845c is even better than the b. Not sure what casouza has experienced but I and most others have found telefunkens to be king of the hill. There is a reason that they command the big dollars. Tried Amperex orange globe and found them to be more aggressive in the highs which may or may not be a good thing.
The 6SN7 comparison/info reference, that I had posted above, seems to have been eliminated. Here's another site, with the same data: (http://www.head-fi.org/t/117677/the-reference-6sn7-thread)