This applies to all interfaces
Constant static noise or hum apparent in your monitors connected to your interface is often caused by a ground loop. A ground loop occurs when there are multiple paths to ground between two or more pieces of equipment. These paths create a loop which causes electrical interference in the form of an unwanted current through a conductor. This is often due to poor wiring in power sockets or extension cables.
Whilst a ground loop is not hazardous, it can manifest itself as a constant low frequency buzz or hum through your audio equipment, or even glitches in audio that are often associated with mouse movement or hard disk activity.
To diagnose your system with ground loop hum, it would be preferable if you could test your interface with different cables in a different location - if the issue is caused by poor wiring in the power socket then you should find when testing in a different location that this noise does not occur. Also, if you are using a laptop, you may find that the hum stops when the laptop’s power cable is disconnected.
Most commonly, ground loops can be solved by using balanced cables. This is why you are unlikely to hear ground loop hum through your headphones but you will be able to hear it through your monitors if you are using unbalanced cables. All 1/4” jack line outputs of any Focusrite interfaces are balanced outputs, which means you can use balanced (TRS) jack cables to connect your monitors to your interface. In most cases, this should prevent ground loop hum.
If you have several units in your setup then one of these units could be causing a second ground path which would cause ground loop hum. To narrow down which unit is causing the problem, have your system up and running and physically disconnect each unit one by one to see when the noise stops.
If the ground loop is apparent in your headphones, is not fixed completely in your monitors by using balanced cables and you are unable to find the source of the second path to ground in your set up, you can get ground loop isolators such as the ART Cleanbox II that work to prevent audible ground loop issues.
If you are unable to solve the hum in your monitors, please contact Technical Support for further assistance.