The function of the X series DAPs' relay

FiiO-Shadow

Q: The function of the X series DAPs' relay

A: The amplified output of the X series DAPs is sent to headphones via an output relay.  In the process of turning on and off and when headphones are being plugged in / removed, the X series DAPs will briefly disengage the earphones from the amplifier.  Thus the pops and crackles of on / off transients and of plugging in and removing earphones from a powered amplifier are avoided.  However, as the relay is an electronically triggered mechanical switch, a slight sound will be emitted, both from the connected earphones and from the X series DAPs themselves.

P.S. The X1 does not have the relay.