Matched Pair RCA 5963 12AU7 12AU7A Vacuum Tubes Black Plate Industrial-Grade US-Made OSC They are dead quiet when

They are dead quiet when the preamp is muted and sound good even with 6

new in box Sylvania 12AV5GA tubes tested to spec on our Paul Hart-calibrated TV7/U

They have narrow gray plates and O getters

This Emerson 117N7GT tube -- and another just like it -- tested to spec on our Paul Hart-calibrated TV7/U

new in box RCA 21LU8 tube tested to spec on our Paul Hart-calibrated TV7/U

Matched Pair RCA 5963 12AU7 12AU7A Vacuum Tubes Black Plate Industrial-Grade US-Made OSC They are dead quiet whenThis matched pair of RCA black plate 5963 dual triodes was tested on our Paul Hart calibrated TV7 U and our Maxi Preamp II for shorts, gas, noise, transconductance and gain. There were no shorts, noise or gas and they tested as follows: Tube One: Noise: 84. 6 dB 85. 56 dB ( 92 dB is the Maxi Matcher's noise floor) Transconductance (Maxi Matcher): 1877 1882 Transconductance (TV7 U): 59 65 where minimum (65%) is 50 50 and 100% is 77 77. Gain (Mu (): 16.