What you are likely experiencing is commonly called “ground loop”. All devices in your studio should be connected to the same ground. If this is not the case and if one or more of the devices are getting their ground from somewhere else, (e.g. from a different power outlet that is running on a different electrical circuit) and devices with different ground are connected to each other (e.g mounted to the same rack rail), this type of noise might occur.
There are different ways to fix this type of problem. The easiest and most cost efficient way is what is called a “ground lift” in order to interrupt the “ground loop”. Not all devices work correctly with lifted ground and might overheat and/or create an electric shock hazard. Before lifting the ground on any device, please contact it’s manufacturer in order to find out if this device will work properly and if it will create an electric shock hazard under these conditions.
Depending on the amount of devices in your studio, it might be hard to find the device that is causing the problem. For this reason we suggest the following approach in order to detect the source of the problem:
1. Disconnect ALL peripheral devices from the computer except for your audio interface and speakers. Printers, network, antenna cable to a TV Tuner card, audio cables etc. should all be physically disconnected from the computer.
2. Check if the noise is still there. If not, skip to step 3 in this guide. If yes, continue with number 2a.
2a. If you are using a Laptop, unplug the power supply and run on battery power. If this resolves the problem, you will have to lift the ground on the laptop’s power supply. (IMPORTANT: Contact the Laptop’s manufacturer to find out if lifting the ground is supported on this device).
2b. If you are using a Desktop computer, while you can hear the noise or have audio playing, turn your Monitor off, and then disconnect it’s power cable. If the noise is gone, you will have to lift the ground on the Monitor. (IMPORTANT: Contact the Monitor’s manufacturer to find out if lifting the ground is supported on this device). If the noise is still there, reconnect your Monitor, turn it back on and go to the next step in this guide.
2c. If your audio interface has a headphone output, disconnect the powered speakers or power amp with speakers from the interface and check if the noise is audible on the headphones. If the noise is gone, you will need to lift the ground on the powered speakers or amplifier (IMPORTANT: Contact the Monitor Speakers / Power Amp’s manufacturer to find out if lifting the ground is supported on this device).
3. If disconnecting all devices resolved the noise issue, start adding one device at a time and check if the noise reoccurs. Then, lift the ground on the device that made the noise problem reoccur. (IMPORTANT: Contact the manufacturer of the device you determined is causing the ground loop to find out if lifting the ground is supported on this device).
GROUND LIFT PROCEDURE:
IMPORTANT: Before you proceed, make sure that you have contacted the manufacturer of the device you intend to lift the ground on. If this is not supported for this device, lifting the ground can cause damages, serious injuries or death!
The best way to lift the ground on a device is to use a 3 prong to 2 prong adapter. These are available at electronic stores such as Radio Shack or Home Depot etc. Simply plug the 3 prong power cable in the adapter and the 2 prong end into the power outlet.
A picture of a common ground lift adapter is below.