Sylvania 12AV7 Vacuum Tube Black Plate NOS-Testing Sylvania NOS-Testing This lot of six Sylvania

This lot of six Sylvania number / type 58 stamped- / engraved-base tubes was tested on our Paul Hart-calibrated TV7/U for shorts

new in box Amperex 3A2 tubes tested to spec on our Paul Hart-calibrated TV7/U

These six US-made 6S4A tubes were tested on our Paul Hart-calibrated TV7/U for shorts

Tube One measured 1940 micromhos

steel plates and steel suppost rods

Sylvania 12AV7 Vacuum Tube Black Plate NOS-Testing Sylvania NOS-Testing This lot of six SylvaniaThis new old stock testing Sylvania 12AV7 dual triode was tested on our Jackson for shorts, gas and transconductance. There were no shorts or gas. Transconductance measured 116% 104% where minimum (65%) is 70% 70%. This tube has black plates; a horseshoe getter and terrific flashing. I am playing it in Bottlehead Crack headphone amplifier as a 12AU7 substitute and it sounds excellent. WE HAVE SCORES OF THOUSANDS OF VACUUM TUBES. IF IT'S NOT LISTED, WE