The PF-50T's tubes are all from Ruby Tubes. There's a a pair of 6L6GC-MSTR power tubes and three nine-pin preamp tubes - two 12AX7s, with one for preamp and gain in V1, and the other handling EQ and amp drive in V2, and a 12AU7 in V3 that functions as a phase splitter for the power amp section. The PF-20T uses a similar all-tube setup, but with two 12AX7's and a pair of 6V6 power amp tubes. All the tube sockets are ceramic, and tube retainers are provided for the power tubes, with shields for the preamp bottles.