This is a collection of more detailed vacuum tube descriptions, explanations, and general information. We hope to continue to add to these links over time.
Telefunken tube date codes
If you are fortunate enough to have some Telefunken tubes with labels that are intact, here is an explanation of how to determine when they were made. This article includes a corrected version of the date code chart originally published by Eric Barbour.
Power tube matching process
Description of our custom test fixture for power tube matching after the tubes are tested on our Amplitrex AT1000 testers. This fixture is a complete amplifier circuit with AC input and a huge output transformer so the tubes can be load tested with a signal generator.
Interpreting Amplitrex AT1000 tube tester results
The AT1000 tester has two bias modes that function very differently and produce very different test results. This article offers detailed descriptions and examples for each bias mode and explains how to interpret the test scores they provide.
The limits of the “bucket method” for power tube matching
Describes the drawbacks of the "bucket method" for power tube testing and matching, and encourages precision power tube matching that is based on the operating conditions of the user's tube amplifier or other equipment.
Genalex Gold Lion EL84 / N709 reissue -- just another Sovtek EL84?
Photos and chart comparing the Russian-made Genalex Gold Lion N709 / EL84 reissue with the current production Sovtek EL84 and vintage British CV2975 (similar to the original Genalex EL84 / N709). This comparison only covers the external structural differences. As for sonic differences -- let your ears be the judge!
TC Tubes specializes in precision testing and matching of vintage and new production vacuum tubes for guitar & bass players, audiophiles, and DIY tube audio enthusiasts. Our website features secure payment options and fast, convenient shipping around the world.