This new old stock-testing matched pair of milspec / industrial GE JG-5814A / 12AU7A dual triodes was tested on 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: -83.4 dB / -85.4 dB (-92 dB is the Maxi-Matcher's noise floor)
Transconductance: 1284 / 1432
Gain (Mu (µ): 17 / 17.3
Tube Two:
Noise: -85.4 dB / -85.6 dB
Conductance: 1475 / 1690
Gain (Mu (µ): 17 / 17.3
These tubes have gray plates; copper support rods; triple crenelated mica spacers and two additional vertical support rods for enhanced ruggedness and no microphonics; slanted-D getters; acid-etched lettering with a circle just below "5814A," and excellent flashing.
I have played them in my Alan Eaton single-ended 45 amplifier with adapters (not included) and they sounded outstanding. They were dead quiet when the preamp was muted and had excellent frequency response, sound-staging, and dynamics.