I have also observed the loading effect via oscilloscope of connecting a low impedance device like a cheap pair of headphones to a line output port. A regular Line Out is not supposed to supply any current at all (ideally); the ideal op-amp has infinite input impedance it draws no current from the input device. Which is precisely the point of the operational amplifier (within a Line Input) - to produce an output signal without drawing current (loading) from the previous components.
A line input has a typical impedance of 10kΩ - compare that to the impedance of typical headphones.
Headphones will draw a huge amount of current vs a line connection, and may end up damaging components due to the current draw.
Bookmarks