On the amp side, you would use a mono 1/4" Jack into the Line 2 output. On the mixing console side the same can be used as the signal is mono. However it is always a question what the aim is, using the console. To note, Line out 2 is the signal addressing the power amp, which will be around or above +4dBU. While Line out 1 is the same signal reduced to be in the range of -10dBV.