Well, one of my favourite preamps (Atma-sphere) uses 6sn7s, but my other favourite tube preamp (Joule) uses 6350s which I never heard of - I think they were designed for TVs, not sure, but it sure does make for a nice sound preamp. My other tube preamps have used 6922s and/or 12AX7s. The old ARC SP6 used all 12ax7s I think, and for the time it was a might fine sounding preamp.
