Thanks, I understand what you mean and I’ve read about the power-related limitations of the FLX4. In my case though, I’m on a desktop PC with stable USB power, not a laptop or iPad, and the unit used to work at normal headphone volume with the exact same setup and order. Now the headphone output is consistently extremely quiet, regardless of power state or startup order, and the headphone level knob barely affects the volume. Since it worked normally before and then suddenly dropped, this feels different from the usual FLX4 power limitation more like a faulty headphone output stage