Match Pair Amperex 12AT7 ECC81 Bugle Boy D Foil Get 539c & Maxi Tested NOS NIB O

(TK1 Delta 71) Matching codes also. Very nice printing. Hickok 539C and Digital Maxi-Preamp 2 Tested. Gain: (51.9 & 48.3 and 53.3 & 54.6) MU and side balance. Mutual Conductance (GM)Test: 72.5 & 82.7 and 72.2 & 64.2 (60 = NOS AVERAGE & 41 = Good MINIMUM).

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