Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing CAL 403 I have played it in

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

This lot of seven GE new old stock

This lot of fourteen RCA 6AG7 tubes were tested on our Paul Hart-calibrated TV7/U for shorts

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

Both are acid-etched

Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing CAL 403 I have played it inThis 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