Sylvania 12AV7 Vacuum Tube Black Plate NOS-Testing Sylvania NOS-Testing These six US-made 6S4A tubes

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

Three are GE and two are Sylvania

perforated plates

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

BECAUSE OF THE BIZARRE

Sylvania 12AV7 Vacuum Tube Black Plate NOS-Testing Sylvania NOS-Testing These six US-made 6S4A tubesThis 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