Riverstone Audio - Matched Pair (2 Tubes) 9-Pin GE NOS/NIB JAN 5670W Fully-Tested Vacuum Tubes 6N3, 6N3P, 2C51 5670 396A Tube Upgrade/Replacement - 5670W Platinum Grade Pair

A pair (2 tubes) of closely matched mil-spec 9-Pin GE JAN 5670W vacuum tubes. These platinum grade tubes have undergone detailed testing and audio testing. The vintage NOS GE 5670W tubes were obtained from factory sealed boxes and are a low-noise replacement for 2C51, 396A and other 5670 tubes. 5670W tubes are also often used as a replacement for 6N3 and 6N3P vacuum tubes (please note that the glass envelope of the GE 5670W tube is approx. 5 mm shorter than 6N3 and 6N3P tubes). The "W" designation in the 5670W tube number refers to ruggedized, military grade tubes; better quality control and internal design changes to enhance reliability. We test/match all 5670W vacuum tubes using Amplitrex AT1000 tube testers. Testing is performed using auto-bias mode (plate voltage is fixed at 150 V and plate current at 8.2 mA); grid voltage is measured to determine deviation from expected NOS level. Vp versus ip curves are also examined to determine balance between tube sections and overall tube performance (Vp-ip curves are generated under fixed-bias mode). Additional quality checks include shorts/leakage, gas, noise and a life test. These vacuum tubes are well balanced between tube sections. All tubes in our matched tube sets are guaranteed to test at NOS (new old stock) levels. Tube boxes are clearly labeled with test conditions, mutual conductance, grid voltage and gain. Vacuum tubes that show even the slightest abnormality in the quality checks, are rejected by us. PLEASE NOTE: These vintage vacuum tubes were obtained from sealed/unopened military surplus boxes. However, because of long term storage, transportation and handling during testing, the silk screen print on the tubes may show slight fading or abrasion. All vacuum tubes tested and matched by Riverstone Audio will have the Riverstone name and logo on the boxes. PLEASE NOTE: 5670W tubes can only be used to replace 6N3, 6N3P, 2C51, 5670 and 396A tubes - DO NOT USE to replace other types of vacuum tubes.