A method and apparatus of load detection for an audio amplifier system is described. A load detector (300) includes a first load terminal (Vp) and a second load terminal (Vn); a controller (302) coupled to the first (Vp) and second (Vn) load terminals and configured to in a first control loop (344, 308, 338), vary a first current (332) supplied to a first load terminal (Vp) dependent on the difference between a first reference signal and the detected first load terminal voltage (312); and in a second control loop (346,306,340), vary a second current (336) supplied to the second load terminal (Vn) dependent on the difference between a second reference signal and the detected second load terminal voltage (324); and to determine a current through a load connected between the first load terminal (Vp) and the second load terminal (Vn) from the second current value (336), and a voltage across the load (344) from the detected voltage difference between the first load terminal voltage (Vp) and the second load terminal voltage (Vn).