Unfortunately I haven’t tried an android. I do not have one available. I thought it’s strange how I hear the crackles both through Bluetooth and through usb, both using iPhone. So it very well could be my iPhone. But I’ve used someone else’s iPhone to rule that out and had the same issues.
I’ve used different iPhones, different cables, different streaming apps, etc. and everything points back to infotainment issue. Unless it works fine with android, then that would point to a glitch in iPhone software since both iPhones showed same issues.
Only other answer could be an amplifier issue. Improper grounding, tuning, interference, unstable power supply, etc. But I don’t think it’s an amplifier issue due to how it only happens when music is playing. Usually with an amplifier issue, you’d hear clipping or feedback even if you paused the input music.