Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing CAL 403 These three GE 6BC5 tubes

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

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

This new old stock-testing National Union globe / balloon-style bottle number 36 tube tested 42 on our Paul Hart-calibrated TV7/U where minimum (65%) is 26 and 100% is 40

I have played it in my Schiit Vali 2 headphone amp and it sounds great

Both are acid-etched

Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing CAL 403 These three GE 6BC5 tubesThis 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