Class XD (crossover displacement) is a proprietary and patented[1] amplifier technology developed in-house by Cambridge Audio.
"[4] Class A amplifiers avoid crossover distortion (because the transistors are always on) but at the expense of generating a lot of heat.
At one unique value of quiescent current, the distortion produced is minimized, and this is what characterizes optimal Class B.
This is the basic Class XD principle, to develop a topology that displaces the crossover point to one side of zero crossing – it can be either positive or negative.
This is achieved by the injection of an extra current into the output point of a conventional Class B amplifier.