Sylvania 7F7 Vacuum Tube Sylvania 3E6 NOS NIB each with two rectangular holes

each with two rectangular holes

(New US-made 7408s typically test with plate current from the mid-teens to mid-30s with transconductance from 2300 micromhos or so

It sounded great in my Bottlehead

new in box Sylvania 6V4 / EZ80 rectifier tube tested to spec on Paul Hart-calibrated TV7/U

a good-very good logo

Sylvania 7F7 Vacuum Tube Sylvania 3E6 NOS NIB each with two rectangular holesThis Sylvania 7F7 was tested on our Paul Hart calibrated TV7 U for shorts, gas and transconductance. There were no shorts or gas. It measured 42 44 where minimum (65%) is 33 33 and 100% is 51 51. I have played it in my Cern Audio phono pre preamplifier as a 6SL7 substitute (with an adapter, not included) and it sounds outstanding. It is dead quiet when the preamp is muted and has excellent frequency response, sound staging, and dynamics It is somewhat