Tube Amp Doctor (TAD)TAD is a German company established in 1993 which selects and matches electronic tubes and manufactures musical instrument accessories.
Bias Master™ - TAD, tube tester, with 4 probes
Bias Master™ system BM4 Measures Bias current of the vacuum tubes in your amp. Includes 4 probes and english/german operation manual. The Bias Master™ allows you to monitor the bias current safely and easily. While adjusting the Bias control pot of your amp, the Bias Master™ shows the actual result. This lets you set and evaluate the full reasonable biasing range your amp and tubes offer to find and set your personal perfect choice.