If you want to split the signal to go to two amps or something like that, simply using the left and right outputs will probably be the best way to go. Some of the effects are stereo, so the signals won't necessarily be exactly the same, but they would sound great with a dual amp setup. If you actually do want to send the exact same signal to both amps (or whatever it you're sending the signal to) the correct way to do that would be to get an A/B/Y box or other active splitter box and take the output from the left output and split it into two mono signals.