Agree with Peter's recommendation of Red Base RCA 5692.
I have tried other NOS RCA's, Sylvanias and Raytheons as well as new production Chinese tubes and the Red Base 5692 were the best for my Cary SLP-88 preamp.
I have tried other NOS RCA's, Sylvanias and Raytheons as well as new production Chinese tubes and the Red Base 5692 were the best for my Cary SLP-88 preamp.