4 Tung-Sol 6K6 6K6GT Vacuum Tubes Black Glass Lot Of Four NOS-Testing 25BK5 Transconductance measured 41/49 for Tube

Transconductance measured 41/49 for Tube One and 44/44 for Tube Two where minimum (65%) is 32/32 and 100% is 49/49

The Bottlehead calls for a 12AU7 which is a pretty-different tube

This GE 11BT11 tube tested to spec on our Paul Hart-calibrated TV7/U

though is not recommended for this headphone amp which was designed for 12AU7s

This matched pair of Philips Miniwatt PCF80 / 9U8 tubes was tested on our Paul Hart-calibrated TV7 for shorts

4 Tung-Sol 6K6 6K6GT Vacuum Tubes Black Glass Lot Of Four NOS-Testing 25BK5 Transconductance measured 41/49 for TubeThis new old stock testing lot of six Tung Sol black glass 6K6GT tubes were 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 and they measured as follows (from left to right, top to bottom): Tube One: 31. 8 milliamps' plate current 2170 micromhos; Tube Two: 35. 1 1980; Tube Three: 40 2120 and Tube Four: 42. 1 2260. New nominal