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Penta Laboratories

12AX7 / ECC83

39.00 USD

Top of the line audio tubes manufactured by Penta Laboratories in China. These fine miniature glass 9 pin double triode amplifier tubes come with short gray plates and chrome tops. Suitable for all audio applications, these fine tubes are printed in yellow with Penta Laboratories logo, 12AX7 PENTA LABORATORIES, MOORPARK CA, U.S.A. MADE IN CHINA, and coded 2239. Boxes are standard Penta Laboratories yellow and black printed 12AX7 PENTA.

Tube Matching
Tube Matching
6.00 USD by tube


A tube may have one, two, or three internal sections depending on the purpose of the tube; somtimes these sections are all the same, sometimes they are different. Due to manufacturing and material tolerances, there may be slight differences between the original specification and the actual tube. Tube matching tests each one of these internal sections and selects tubes, compared to original specifications at manufacture, for balanced performance and good sound.


All our tubes are tested by us prior to packing on our Stark, AVO, Simpson or RF Laboratories Inc. calibrated testers. On request for tube matching, tubes are matched for Mutual Conductance in Micromhos and Plate Current in Milliamps on our Amplitrex or Radioelec Duovac testers, with results printed for each  individual tube. Certain tubes difficult to test are matched for Mutual Conductance in Micromhos only on one of our regular calibrated testers. On request we can also test for Microphonics.


20 Items

Data sheet

9 pin miniature Noval B9A
Boite type
Double Triode
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