Q: “I’m trying to connect the balanced output of a DAW interface to the unbalanced line input of a mixer. The mixer can work with the +4 dBu operating level just fine, but what’s the best way to unbalance the signal?”
A: There is no single universally correct answer to this question. The correct answer will depend on the specifics of the equipment in question. What usually works best, and is usually the first thing to try when experimenting, is to float the cold (or minus (-)) lead from the balanced cable. So the hot, or positive (+) lead from the balanced output will connect to the hot of the unbalanced input, and the shields will be connected together. Normally you do not want to allow the cold (-) lead to run the length of the cable because it will act as an antenna that could pick up stray EMI and feed it back into the output.
If you try floating the cold (-) and get a lot of hums or strange behavior you can then try to short the cold (-) lead to the shield. In some circumstances the best performance will come from connecting the hot (+) as normal, connecting the cold (-) to the shield of the unbalanced input, and then floating the shield from the balanced output – in other words, run it the length of the cable, but don’t connect it. This is similar to, but not exactly a telescoping shield configuration that’s often used on balanced connections.
If your balanced output employs an impedance balancing architecture you should be able to connect a normal unbalanced cable, or you can simply short the cold (-) to the shield at the output.
If none of this is acceptable in terms of hum and noise you’ll probably have to resort to a transformer of some sort.