I shall try to restrain myself, because this is a symptom (probably) of 'kinda' balanced lines. Given a true balanced line (the signal is defined as the difference between the two legs), if one side is open (unterminated) the signal is undefined. Without getting into it too far, it will sound like crap. A 'kinda' balanced line (differential output) may sound alright, but will lose 6dB under two conditions. First, if you feed an unbalanced input, half the signal will short to ground. Hence -6dB. You will also observe the same effect if one leg is simply disconnected. A true balanced line (requiring a transformer or some clever electronic bits) does not behave thusly. Here's the real news: Digidesign and most current manufacturers do not use real balanced outputs. (They're more expensive to manufacture.) This means it's impossible to mix balanced and unbalanced gear in a patch bay without associated 6dB losses. Bit of a mess, wot?