These feature the classic split top glass and long 17 mm plates that identify Blackburn production. Key specifications include a 6.3 V heater at 0.3 A and two independent high-mu triode sections. This is a very early production pair from the Blackburn factory.
This has a halo getter and a December 1958 date (B8J). This was tested on our Triplett 3444A tester with results of 1400/1450, where 1600 is the average new value. Do not buy this item and then ask us to falsify the forms.
The B&K 700 operators manual states the minimum/good range for a 12AX7 tube is a reading of 22. A reading of 22 is equivalent to 60% Gm. This tube, testing at 29/28 is a good tube considering new 12AX7’s normally test 32 and above.
Rare variation Both have matching B9B dates Both tested strong using an Amplitrex AT1000 with the following results (as photographed): Tube 1- 91/116% ip 81/100% gm Tube 2- 91/91% ip 87/93% gm
Mullard(fisher) 12ax7 tube in good condition.test good.