Procedure

If you want to send a mono signal to both channels of a GXD amplifier, you need to send the mono signal into the XLR input of channel 1, then use the 1/4 inch input of channel 1 to jump the signal to either the 1/4 inch or XLR input of channel 2. The XLR and 1/4 inputs are parallel on both channels, so you can feed the signal into one and send that signal out of the other input.