Hack for reducing hum

[Omega_Void]

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.

 

[Omega_Void]

BTW, you don't actually need signal on both lines to do this. Just similar cables on each input plugged into similar outputs (in which case you don't need to use a polarity-inverted cable).

Using signal on both lines is preferred though, 'cos it improves your SNR by 3dB, whereas using no signal on one input will degrade your SNR by 3dB, which may or may not be preferable to the hum you're getting rid of.