A Comparison of Current Production 12AX7 Tubes 2013 Graph Interpretation All 12AX7s have an amplification factor (μ) of 100 ("high-mu"). Ideally, every 12AX7 should yield the same gain when placed in the same circuit. However, in reality there are comparative gain differences amoung 12AX7s. This graph is based on the average gain and noise measured
