The A-138d can be used as a crossfader or as an insert module for external effect units with dry/wet control. If the module is used as a crossfader the two audio signals are connected to In 1 and In 2. The position of the CF (Crossfade) control defines the relation between the levels of the signals In 1 and In 2 that appear at the Mix Output. In the leftmost position of CF only In 1 appears at the output, in the rightmost position only In 2. In the centre position both inputs appear with the same level at the Mix Output, acting like a simple 2 into 1 mixer.
The mute switch can be used to mute In 1 or In 2 independent of the position of the crossfade control. In the centre position it has no function. The controls Atten. and Amp. and the 1/4" sockets FX Send and FX Return are not used in this application.
When used as an effect send/return module the signal that has to be processed by the external effect unit is connected to In 1 with attenuation with the Atten control, before sent to the FX Send. An attenuator allows allows attenuation of the signal.