@salvatore-di-piazza thanks for this detailed list - some of these I’ve tested, some I had not thought about. (The iRig HD 2 has a lightning connection to the iPad).
Another thing I’ll test, the headphone output from the iPad, to see if it shows the switching noise also.
And , just for anyone reading, the noise when switching presets is sort of a ‘whoom’ noise, as opposed to say, a ‘pop’.
Ok, So the hd 2 has a lightining connection, I forgot that
Would you record a short video for us showing the noise you've talking about?
plus, I think you could test the virtual volume pedal in Bias fx without necessarily having an expression pedal connected to the BT-4