Hey Pat I am ready to post more about Clarinet tubes....
Originally I built my Clarinet with just the stock JJ 12AU7 plain jane tubes. These cost 9.95 over at tubesandmore.com where I bought my Hammond and stainless hardware.
I tried RCA clear tops, JHS and JAN Sylvanias and GE's, vintage 1950's Mullards, Supratecs, Raytheons, Hammonds, and a few others.
So far for the money the newer JJ 12AU7-S (Long plate) at 13.95 a piece are my favorites. I am sitting close to my speakers, so their warm flowing sound is a little better in my environment than the others I have tried.
On my Clarinet I am running .82uf SIO Mundorfs and .22uf FT-3 Teflons for the final signal cap, and just a pair of SIO 1.0uf caps at the B+. I am finished parts rolling on my Clarinet. It sounds fantastic.
The JJ tubes are so cheap I can just leave the preamp on all the time. It sounds better than waiting a few hours for the tone to bloom.