Amp Frequency (and Phase) Response Chirp

Quick frequency response measurements can be made using the main window of the analyzer while in FREQ RESPONSE mode (that button is located in the GENERATORS section).

Alternately, frequency and phase of an amp can be plotted using the AMP Frequency Response Chirp in the Automated Tests menu. This plug-in also allows the display of phase. The options for the plug-in appears below:

Note that to enable phase measurements, you need to select both the Right Channel as Reference and also Plot Phase. The displayed phase will be the phase difference between the left and right channels. Generally, you'd want to connect the analyzer output to your DUT and also to the right channel. And the output of your DUT would go into the left channel.

A plot of the gain and phase of the QA40x Audio Analyzer in loopback is shown below. The phase is flat at 0 degrees across the spectrum:

A plot of the gain and phase of a balanced high-Q notch is shown below.

If we use the other input of the balanced high-Q notch, we get the following plot, which indicates a 180 degree phase inversion: