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Change cable placement
If power cables and audio cables are placed near each other it can cause noise in the audio. Try to have as much distance between the DacMagic 100 and other power cables.
A single perpendicular crossing of power and audio cables is much better than having them in parallel.
If you must have them in parallel, leave as much space as possible between the audio and power cables.
Try securing the analog inputs
The humming or buzzing sound might be due to the fact that the analog inputs are not fully connected.
Please make sure that the cables are connected securely to the inputs.
Switch from grounded to lifted
Try to switch from ground to lift using the switch on the back side of your DacMagic 100.
NOTE! It is recommended to use the ground setting unless it causes noise in the audio.