Matching 12AX7 Vacuum Tubes on a Tektronix 576 Curve Tracer
The Tektronix 576 curve tracer, originally designed for matching transistors, can be modified to match vacuum tubes. Unlike a tube tester, the curve tracer can operate a tube at maximum rated plate voltage, at up to 10 different negative grid bias settings, all at once. The results are plotted on the screen as curves representing the plate voltage as horizontal, and plate current as vertical, with 10 different grid bias points on the screen at the same time! Matching tubes is simple this way, and far more accurate than using a tube tester.