I have solved a problem for me and think the world could also use that solution. 
SPLMeter is a Sound Pressure Level (SPL) meter, available as a macOS/Windows/Linux standalone app and as VST3 / AU plugin. It works in real time or from pre-recorded files. It can do the A, C weighting stuff, but a FFT, logger and psychoacoustic value calculation for values like Loudness, Roughness or Annoyance are also included. Some stuff you not see every day.
Since SPLMeter supports ASIO on Windows, you can use your QA40x with the app, too.
Download latest release here:https://github.com/ppklose/ppkSPLMeter/releases
More infos and readme here: https://github.com/ppklose/ppkSPLMeter