By "having two inputs going into the same channel of an amplifier could be bad" means that if your amplifier has both balanced and unbalanced inputs, you do not want to use both at the same time. The 7700 is such an amp. Even though you have to flip a switch to select either balanced or unbalanced, don't connect both. This applies to each channel - you could connect some channels with unbalanced cables and other with balanced, but don't connect both types of cables to the same channel.