Question about BC21 6sn7 tubes

I was wondering if someone out there could direct me to a reference that would explain to me the differences between the various 6sn7 tubes. I just bought a BC21 and am new to tubes. Is a 6sn7 the same as a 6sn7w, 6sn7gta, 6sn7gtb, vt-231?

I did a search in the forums and found some bc21 owner's favorite 6sn7 tubes from which I can kind of deduce substitutions but thought maybe there was a more definitive list somewhere.

Many thanks in advance.
Hi Tooter,

I've owned a BC21 myself for 2 1/2 years and have enjoyed greatly. Along the way I've bought bunch of different NOS 6SN7s such as the Sylvania, Ken-Rad, Raytheon and RCA VT-231s, and other variants of 6SN7s like Tung-Sol and GTs and GTBs.

Although I still haven't gotten around to trying them all, I do have some favorites. The ones that are currently in my BC21 are the black glass variant of the Ken-Rad VT-231. As many people have noted they create a very large soundfield, have great dynamics, great bass and are more organic than the Sylvania VT-231s.

The Sylvanias offer a bit more top end extension and slightly more air. Which one you end up liking will depend on your taste and associated equipment, I just seem to gravitate towards the WWII military versions.

Although I'm not aware of any definitive 6SN7 listing, the links Albert supplied will help a lot, and you can always look up Andy at Look under octal tubes and you'll find a pretty comprehensive list along with production years and tonal characteristics.

Good luck!
Actually, when it comes to this preamp Sugarbrie is the man to ask here on the 'Gon!
Thanks to all for your suggestions.

I guess what I was really trying to ask is that since the various 6sn7 tube types are different electrically can they be interchanged freely in a BC21. Based on the above posts from BC21 owners it seems so.

I am loving my BC21 and looking forward to diving into tube rolling. Right now my BC21 has the stock philips tubes and sounds very good to my novice ears. Even though this pre has its "faults" like any other piece of audio component I'm able to hear past them and still enjoy the music, something I've noticed about Blue Circle equipment in general.

Thanks again.
The stock Philips tube are actually pretty good. I think Rogue use to include them with the "upgraded" version of the Ninety-Nine preamp....

The BC21 is a very simple design, so you are listening to the tube itself in many respects. That makes it a fun unit to roll tubes with.