6P14P-EV is an aexcellent tube to use in audio amplifiers, it has 5000 hours lifetime guaranteed by manufacturer and is the same tube/direct replacement with EL84, EL84M, 6BQ5 etc. Each tube is heated for at least 30 minutes, listened in an amplifier with plate current monitoring and a 1 kHz oscilloscope view of a sine wave. After that each tube is tested using L1-3 or L3-3 tube tester, first for shorts, leakage heater-cathode and Ig1 no more than 0.1 micoA and then are meaured plate current and transconductance. The sorting of tubes in pairs or quads is done taking into account both the anode and the transconductance. For example, in a pair of 0% both tubes have exactly the same anode current and the same transconductance at the test conditions: Up=256V, Ug2=256V, Uh=6.3V, cathode biasing.
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