(1 Pair) 31 RCA/Cunningham NOS 1930's - 1940's (12.0ma and 13.2ma) (Same Gm)
$ 34.99
1 pair) 31 RCA/Cunningham NOS 1930's - 1940's
1 tube) 12.0ma and Gm=1100 RCA/Cunningham engraved base
1 tube) 13.2ma and Gm=1100 RCA red print taller bottle
Tested on Amplitrex
Vplate=180V
Vgrid=-30V
Good NOS Ma = 11 -12ma
Good Gm = 1000
See more: vacuum tube
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 31 RCA/Cunningham NOS 1930's - 1940's (12.0ma and 13.2ma) (Same Gm)&Category=vacuum tube&ImageURL=http://tubeworldexpress.com/cdn/shop/files/1_6b0e4821-d619-4243-8992-d243883ee45b.jpg?v=1683736885){kind=link}
 31 RCA/Cunningham NOS 1930's - 1940's (12.0ma and 13.2ma) (Same Gm) "Pin It")