Power tubes (also called output tubes) are matched using a tester that tests the tubes at high plate voltages, as well as various bias voltages. This means that when you install these tubes, they will be a tight match inside your amplifier.
We have very strict standards when it comes to matching. We match power tubes within 5% for plate current (Ip), and 10% for transconductance (Gm). Most other retailers will match to just one of these values however it is important to have both of these values matched. This is a process that takes lot of time and dedication since tubes can vary so much from the factory.
After testing the tubes we will match them in pairs, quads, sextets, and even octets. We write the plate current and transconductance values on the box so you know exactly what you are getting.
Lastly, the tubes are checked for shorts and leakage on an Eico 667 tube tester before the tubes are shipped out.
Preamp tubes (the smaller tubes) are placed in a tester that tests for the gain (µ) and conductance (Gm) of the tube. For dual-triodes (12AX7, 12AT7, 12AU7, etc.) both sections of the tube should be balanced to a reasonable level. We do not sell tubes that have unmatched sections to a certain degree. We also do not sell tubes that have improper gain levels depending on the type of preamp tube being tested. For instance, 12AX7's should be in the 88-100 range for gain, if it reads below that level then the tube is rejected.
If you buy matched preamp tubes then we match the tubes within 5% for gain, and 10% for conductance.
Rectifier tubes are tested on an Eico 667 to ensure the tube is working properly before being shipped.