Matched Pair RCA 12B4 12B4A Vacuum Tubes Valves Black Plates Copper Support Rods NOS-Testing January 10 2021 It is dead quiet when

It is dead quiet when the preamp is muted and has excellent frequency response and sound-staging

new in box milspec Sylvania JHS-5977 tubes in this lot

These three RCA-MANUFACTURED 6U7 tubes were tested on our Paul Hart-calibrated TV7/U for shorts

GE-BRANDED 17EW8 / HCC85 tubes tested to spec on our Paul Hart-calibrated TV7

I would rate it a 6

Matched Pair RCA 12B4 12B4A Vacuum Tubes Valves Black Plates Copper Support Rods NOS-Testing January 10 2021 It is dead quiet whenThis new old stock testing matched pair of RCA 12B4A tubes was tested on our Paul Hart calibrated TV7 U for shorts, gas and transconductance. There were no shorts or gas. Tube One measured 43 while Tube Two measured 46 where minimum (65%) is 32 and 100% is 49. Wish I could tell you how they sound, but I don't have any equipment that uses these. WE HAVE SCORES OF THOUSANDS OF VACUUM TUBES. IF IT'S NOT LISTED, WE MAY HAVE IT. PLEASE ALSO SEE OUT ETSY