I used Mullard GZ37 and Sophia 274B as rectifiers with good results. I was most happy with 5U4G. I think it was a NOS Ken-Rad. I had also used Phillips, RCA, and Sylvania 6SN7's with good results. The best thing that I tried with that amp was good NOS RCA 2A3's. The Sophia 2A3 globe mesh tubes also were nice.