How We Test

Koray attentively testing a NOS 211 power triode on the Amplitrex and a AVO MKIV aside.

Why the Amplitrex AT1000?

Because, we would like to;

- use a tester designed with audiophile and musical instrument tube testing in mind

- test tubes at real-world power levels, the AT1000 can operate tubes at up to 500V and 160 mA - the power levels output tubes see in real-life, unlike many vintage testers that have only 165 to 250 VDC available for testing

- read true emission results in DC milliamperes, and true transconductance in mA/V (1mA/V=1000 uMHOs) using a 1 kHz AC signal. The Amplitrex offers laboratory grade testing under microprocessor control and makes it possible to check a tube according to the original manufactures design specifications taken directly from vintage tube data books. Many vintage testers were designed for television and radio tube testing. Some do not even test transconductance, or GM, they only measure simple cathode emission. Even some better vintage testers give you the results only in arbitrary, meaningless, units

- measure Heater-to-Cathode Leakage, Emission and Gas thoroughly

- match tubes not only by plate current (emission), but also by transconductance,  and most importantly at normal current and voltage levels, faithfully reproducing the actual operating conditions found in many amplifiers, preamps and other equipment

- be able to listen to tubes for selecting only microphonics and noise free ones to offer the customers

Testing Process
Each tube’s electrical properties are analyzed for heater-to-cathode leakage, shorts, grid leakage (gas test), plate current (emission), and transconductance is measured. Results are noted on a label for each box. Matching is within 10% plate current and 5% transconductance unless otherwise noted. Given the large volume of our stock we often can match much tighter than this.

We screen many preamp types for noise and microphonics on  Maxi-Preamp 2 Digital Tube Tester. This is a very useful gear for the task. Thanks to its very high gain we can detect any noise and microphony both thru its audio output connected to active speakers and digitally on the display as RMS noise. However, even the best test gear combined with the human factor may sometimes miss something. So, we take exchanges if a tube is found to be noisy when installed in your particular application.

Testers under use:
Amplitrex AT1000
Maxi-Preamp 2 Digital Tube Tester
Hickok Military TV-2 and several TV-7 types
Hickok 752A
B&K 550





Maxi-Preamp 2 Digital Tube Tester

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