Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing CAL 403 12AT7s are notorious for their

12AT7s are notorious for their unmatched triodes and their deviation from nominal parameters

This almost-perfectly-matched pair of Sylvania black plate 6C4 triodes was tested on our Paul Hart-calibrated TV7/U for shorts

The spine is in fine shape with no loose pages and the dust jacket is without nicks or tears

new in box RCA 6GK5 tubes tested to spec on our Paul Hart-calibrated TV7/U

These three GE 6BC5 tubes tested to spec on our Paul Hart-calibrated TV7/U

Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing CAL 403 12AT7s are notorious for theirThis matched pair of GE MANUFACTURED 6K6 6K6GT tubes was tested on our Maxi Matcher 2 with 325 volts on the plates and a bias of 36 volts for shorts, gas, plate current and transconductance. There were no shorts or gas. Tube One measured 1940 micromhos, 29. 3 milliamps' plate current. Tube Two measured 1880 31. 8. New nominal is within one standard deviation of 1900. These tubes have copper support rods; rectangular mica spacers; black and silver