The TAD Premium Tube Series, the "STR-Series" is manufactured exclusively for TAD in a contract factory according to individually defined specifications. They thus follow the most sought-after historical designs from the heyday of the tubes and correspond to their tonal structure, dynamics and convey an authentic playing feel.
For the selection and quality control of the "STR tubes" we have developed and built our own testing systems, which allow us to test the tubes in real amplifier circuits, under real conditions with voltages up to 600 V. Further tests for consistent parameters, mechanical as well as electrical, power test, continuous full load test, mechanical load capacity and of course the sound aspects in different amplifiers follow.
Each TAD tube is tested. Each pentode goes through an optical test, is tapped while operating on microphony and at the same time is monitored for noise, hum and interference via a monitoring system. Only then are the parameters measured and matched according to Ia (PC) and Gm (TC). Each test series includes 400-500 tubes to achieve the tight tolerances of 0.5-1 mA (PC).
The actual tests require a proper burn-in of the tubes to ensure stable cathode emission. Since this is usually not the case ex works, we have developed our own burn-in system.
All TAD tubes and boxes are labelled with PC and TC values and are given a serial number to identify each tube we have ever tested. We constantly check the quality of the selection and matching of the TAD tubes ourselves, as our service workshop uses TAD tubes on a daily basis and we also install them in our TAD amp kits. Thus, TAD has a complete quality assurance system for amplifier tubes - at TAD in Germany.
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