If you are using a USB Audio connection:
Make sure you are using a certified cable for USB Audio, preferably one that displays an official mark. If you are using USB 2.0, the cable should be "Hi-Speed USB" certified.
Make sure your USB cable connection is not longer than 3m. This might cause suboptimal audio quality.
If you are using the optical or coaxial inputs:
Ensure that the cable is securely connected to the source equipment and DacMagic 100.
For optical connections we recommend the use of high quality TOSLINK fibre-optic interconnect cables, specifically for audio use.
For S/P DIF coaxial connections we recommend the use of a high quality 75 ohm digital RCA interconnect cable (not one designed for normal audio use).