As I recall, both sets (upper and lower) of outputs are the same. This was done to facilitate direct connection to speakers with bi-amping capabilities. The H (high) is for the positive (+) side of the speaker; and the L (low) is for the negative (-) side. Make sure the switch is set to STEREO (not to BRIDGED) and your done. Enjoy the amp; in my opinion, one of the all-time greats!
Ken
Ken