Each vacuum tube is burned-in for a minimum of 48 hours dissipating full power with filament, plate and screen voltages that are normally used in amplifier applications. All of this ensures that the various electrical parameters have stabilized and the matching of each vacuum tube will not drift during the life time of each audio tube.
Our power tubes are matched within 5% variation on all parameters. We start the process by using audio tubes that are tested for bogey values and reject those that are on the outside limits of their design. Each vacuum tube is then tested on our fleet of wt-100a original RCA production testers for plate current, screen current and transconductance (gm). We also check for grid current and leakage between elements.