Graph not plotting phase

QA402, SW v0.9999 I would like to measure DUT frequency response and phase. I’m running the automated AmpFrequencyResponseChirp and ticking the “Plot phase” box, but only gain and frequency is plotted. How can I get it to plot phase?

Here are the settings.

Hi @Bjerre, Yes, I have confirmed and we can fix for release later this week. Thanks for reporting and sorry for trouble.


No problem, thanks.

Btw, excellent produkt!

Hi Matt,

Just did want to measure Amp Freq and Phase response, and did run into the same problem.
Do you maybe know, when this issue will be fixed?



Hi @ttako, At this point it could be a few weeks. The 1.1 release will have the front-panel I2S, but it has run into some issues. I’ll update as I learn more. Thanks!

I’ts been more than a week, and I really need to measure the phase of an allpass filter. Could you just release a phase plot fix straight away?

Hi @Bjerre, if you send a mail to support at quantasylum Jan will send a link to the 1.0 release if the phase measurement if it is urgent. The 1.0 release has the phase measurement and a single fix to correct where UI state could get out of sync with HW state.

It’s had virtually no QA aside from what I’m showing below. Also, if the release asks to upgrade your firmware, before clicking yes or no, unplug your hardware and then click no and contact support.

OK, so here’s how it works in the AmpFreqResponseChirp plugin:

First, you must tick the “Right Channel as Reference” box and the “Plot Phase” box.


Next, your HW needs to be setup as follows, where the LPF in the diagram is any DUT. Of course, you’d want to cap off the L- and R- inputs. More details on making FR measurements with the right channel as the reference as HERE


When the plugin is running, pay attention to the status in the upper left. You want to make sure you aren’t seeing the “FFT too small” warning. Also, note in the plot below the right trace is flat, and the yellow trace shows the influence from the DUT.

In the time domain, this will appear as shown in the plot below. Again, note the red right trace shows zero impact from the DUT, because it’s not passing through the the DUT. Be aware: At higher sample rates there’s a bug where the left and right inputs can switch at power up. If this happens, you’ll see the yellow trace remain flat. In that case, re-plug the box.

I tested a lowpass filter made from a 3.3K and 33nF, with a computed corner at 1.46 kHz. The measurement shows 3 dB point at 1548 Hz:

The automated test shows the correct phase response for a low-pass filter, with a 45 degree shift at the 3 dB point