What amplification class does the EDGE W use?

The EDGE W uses Class XA amplification. For Class XA, the crossover point is moved so that both sets of transistors are always on until the signal reaches a loud enough level.

This means that for low level signals, the amplifier is essentially operating as a Class A amplifier and it is only when the signal is sufficiently loud enough that the transistors switch over. Any crossover distortion is therefore masked within the signal.