Don't know if anyone has done this, but:
Had a problem with hum that wouldn't go away on a balanced line. Suspected it was getting in the soundcard's analogue signal path after the differential input (i.e. not a cable-shielding problem).
Was able to route the same signal to two inputs using a phase-inverted cable for one. Inverted the signal from that input in the DAW and summed the two inputs digitally. Hum went away.
Just something to try if your soundcard may have poor shielding or a pin 1 problem.
Had a problem with hum that wouldn't go away on a balanced line. Suspected it was getting in the soundcard's analogue signal path after the differential input (i.e. not a cable-shielding problem).
Was able to route the same signal to two inputs using a phase-inverted cable for one. Inverted the signal from that input in the DAW and summed the two inputs digitally. Hum went away.
Just something to try if your soundcard may have poor shielding or a pin 1 problem.