This is how I set and ensure stable bias on tube amplifiers. Sometimes new tubes can have drift. They may settle down over time. If you do not monitor it, the tubes could go into runaway, red plating and possibly damaging your output transformer. After performing this exercise, we elected to remove the JJ's and go with Tung-Sol Mullard series. The bias setting and stability greatly increased. Tung-Sols are D-Lab's go to tubes. Note the quick response of the Hioki's monitoring the bias.

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