| Test | 12FK6 12V 330 | 12FK6 13.5V 330 | 12FK6 15V 330 | 12FK6 16.5V 330 |
| Frequency response (from 40 Hz to 15 kHz), dB: | +0.03, -0.02 | +0.04, -0.03 | +0.03, -0.02 | +0.03, -0.02 |
| Noise level, dB (A): | -93.5 | -93.5 | -93.9 | -93.9 |
| Dynamic range, dB (A): | 91.1 | 90.5 | 90.4 | 89.9 |
| THD, %: | 0.289 | 0.882 | 0.641 | 0.598 |
| IMD + Noise, %: | 0.298 | 0.878 | 0.606 | 0.562 |
| Stereo crosstalk, dB: | -90.7 | -88.9 | -89.6 | -90.7 |
