Symptom
An unwanted hum or buzz can be heard in the audio signal.
Cause
This can be caused by devices that introduce an electric potential to the ground connection. This includes:
- Peripheral devices connected to your computer.
- A low quality power supply unit.
- Using multiple power outlets.
- Electrical devices nearby such as fridges, electrical heaters, elevators, fans, dimmer switches, etc.
Solution
Resolving a ground loop requires some investigation. The troubleshooting steps below outline the most common solutions.
Disconnecting your Devices
In order to find out where the ground loop arises, disconnect all peripheries from your main device (i.e. from your computer, mixer or MASCHINE+) but not the amplifier and / or speakers. This applies to all peripheral devices you may have connected (e.g. external harddrives, MIDI controllers, etc.).
To check if the amplifier or active monitors create the ground loop, monitor your audio signal from the headphones output of your device (while the amplifier/active monitors are disconnected).
If you find the device that introduces the ground loop, a ground lift of the audio connection may solve the issue. Never lift the ground of the power connection!
Contact the manufacturer of your device before lifting the ground to find out if ground lifting is supported on your device. Some devices offer a switch for this whereas others may require a modified audio cable or a DI-Box (see Balanced Cables and DI Box chapters at the bottom of this article).
Power Supply
A low quality power supply unit can lead to ground loop noise, particularly on laptops. Disconnect your computer from your power supply so that it runs on battery power and verify if this resolves the issue. If you are going to use a replacement power supply unit, make sure that its specifications meet the ones required by your computer in order to avoid permanent damage.
Shared Power Outlet
Always connect your devices to the same power outlet (e.g. with a multi-outlet power strip). Note that even if the power supply of your laptop computer is not connected, your setup may still be vulnerable to ground noise from an external device with its own power supply.
All devices that are physically connected to each other should share the same power outlet. You may also have to separate polarized plugs (two-prong) from grounded plugs (three prong), by connecting them to separate circuits.
Nearby Electrical Devices
Eliminate the possible sources by disconnecting nearby electrical devices one by one. Alternatively, disconnect all of them and then reconnect them one by one in order to identify which one is causing the problem.
If it is still not possible to identify the cause of the hum or buzz, we recommend testing the device at a different location (e.g. at another house or studio) to see if the issue still exists.
If the source cannot be identified or has been identified but cannot be eliminated, a grounded power supply (one that has ground connectors) should help.
Note: If you are unsure that the electrical system in your house/appartment is properly grounded, you would need to consult an electrician.
Note for TRAKTOR DJs using Timecode Vinyl
If you are using TRAKTOR timecode vinyl, make sure to connect the grounding cable on the back of your turntable with the grounding screw on the back of your audio interface or hardware mixer. If either grounding cable or grounding screw are not provided, please consult the manufacturer of your hardware device for more information.
Balanced Cables
If possible, always use balanced audio cables to connect your audio device to your mixer or speakers. If your mixer provides both unbalanced and balanced inputs, always connect your balanced sources to the respective inputs on the mixer.
DI Box
If you cannot fix the ground loop with the tips above, you can try to put DI boxes in between the connections of your audio devices, your mixer and/or your active loudspeakers. This will break the ground of the audio connection. With a DI box you can use balanced audio cables for unbalanced audio sources. Additionally, most of these DI boxes feature a Ground Lift switch.