(!!) 6EW7 Sylvania BIG BOTTLE branded GE NOS 1960's (3.5/36.5ma)1 tube) 6EW7 Sylvania BIG BOTTLE branded GE NOS 1967 (LW) 1 triode section) 3. 5ma Gm=1700 1 triode section) 36. 5ma Gm=6100 Tested on Amplitrex AT1000 Section 1 reference = 4 6ma and Gm=1700 2100 Section 2 reference = 45 50ma and Gm=7000 8000 (6EW7 is a close substitute to the 6DE7) Woo Audio 6 Woo Audio 6 SE RCA made skinny bottle 6EW7 Sylvania made FAT BOTTLE 6EW7