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 www.vintagetubeservices.com. Look under octal tubes and you'll find a pretty comprehensive list along with production years and tonal characteristics.
Good luck!
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 www.vintagetubeservices.com. Look under octal tubes and you'll find a pretty comprehensive list along with production years and tonal characteristics.
Good luck!