You should measure voltage from amplifier output to get power. Now you are hooked on input voltage. Looks like clamp is on correct wire. Just change voltage probes to amplifier output :)
I have been tackling this issue and have managed a half-fix, it is beacuse these amps use bluetooth chips from jieli which are programmed to give bluetooth priority over aux, and the aux input is super low quality beacuse it goes through a 12 bit adc
I experience too much distortion in bass output... probably preamp is not adjusted properly. To have clear bass I have to turn down way low the bass volume. I hear the same bass distortion in this video..
To test a amp you need a decent set of speakers, your test setup does not even have the speakers mounted in a box! This is a functional test not a quality test. Also, learn your levels, over powering your mic was a rookie mistake.
