Visualizer Residual

The Residual Visualizer allows you to examine what remains of the incoming signal from the DUT when the fundamental is removed. On older analog audio analyzers, there was usually an output on the back of the instrument that was connected after the fundamental filter. And by connecting an oscilloscpe to this port, you could see the harmonic-only content, and learn if the harmonics were due to crossover distortion, clipping distortion or slew limiting. Of course that understanding requires a fair bit of skill.

On the QA40x analyzer, the Residual visualizer applies an deep IIR filter notch to the incoming signal. The center frequency of the notch is determined by the generator 1 setting. What remains are the second harmonics and beyond. In the plot below, you can see the left-channel signal in blue, and the post-filter residual in red. Note the scale of the residual (on the right) is much smaller than scale of the fundamental (on the left).