Now the Type 42 tube is a very early Pentode, first showing up in radios in early 1931. This tube was very popular in early radios, back in the 1930's. It is a very nice tube, and sounding nice and powerful, solid and beautiful to look at. Soon after this tube was replaced with the 6F6 tube. I have the input tube of 6C4 and that basically half of one 12AU7 tube going into the driver tube of 5687 tube, my favorite sounding driver.