I just recieved a pair of NIB WE 350B's today and installed the insanely priced tubes in place of the 6F6G's, currently in service.
Ecclectique is correct, the 6F6G sound very similar to the 350B's with the real difference being a slightly less glorified bass and mid range treatment as noticed on the 6F6G's. It does seem on the surface, that the 350B's tend to have a little more detail, but proper burn-in time will really tell the story. Please note, do not take this comments as gospal as this result is system dependant and also very much dependant on speaker placement in the room. By moving my listening position around 3 feet forward resulted in less of booming effect as noticed with both the 6F6g's and the WE 350B. The booming effect is most likely due to the listening position, where the rear lounge is placed up against the back wall, thus amplifying the bass effect.
So, are the 350B's worth 8 times the asking price of the 6F6G's. Probably not, but don't let that stop you. Try it for yourself, your milage may vary.
Having said that, I still find the lower treble to be a little weak and the bass still not as tight as it could be. This Phenomena is probably due to the Ken Rad VT-231 Black Glass. I've ordered a pair of Tung Sol Round Plates as suggested by Cello, and they should arrive in the land down under in around 10 days. I'll keep you posted as to the results.
I think it's time to seriously start rotating the various tubes in my collection, to hit upon the magic sound I'm looking for, which is probably the same as everyone else's holy grail, Brillant highs, rich mids with strong, deep tight bass.
Note: Tubes Currently on duty in Sauvignon:
Rectifier: Mullard GZ34
Regulator: WE 350B was using 6F6G (Sylvania Green Letters)
6SN7 : Ken Rad Black Glass VT-231
Any thoughts?
Cheers