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GenkiGenkiGenki Instruments

Ground Loop Noise

If you hear a whine, ticking or buzz on Katla’s outputs that changes with what your computer is doing, the cause is almost always a ground loop. It happens when Katla’s Genki Link port and a non-isolated USB audio interface are connected to the same computer. Each device works fine on its own. The noise comes from how they are connected together, and other USB instruments run into the same problem with non-isolated interfaces.

MAINS POWER · CHARGERS · POWER SUPPLIESComputerlaptop or desktopcharger · CPU · USBKatlaaudio ground = USB groundGENKI LINKLINE OUTPOWERAudio interfacenon-isolated USBUSB · LINE INSpeakersor headphonesUSB: data + ground + shieldUSBaudio cableground loopUSB isolatorring broken hereDI boxring broken here
At the interface input
Katla's sound with the computer's noise on top: a whine, ticks or buzz.The isolator passes USB data but not ground, so only Katla's sound arrives.The DI box passes audio but not ground, so only Katla's sound arrives.
What Is Happening
Section titled “What Is Happening”

Every USB cable has a ground wire and a metal shield, so it connects the computer’s ground to Katla’s ground. Most USB audio interfaces are non-isolated, which means they share the computer’s ground in the same way. When Katla’s audio cable goes into that interface, the three grounds form a closed ring.

A computer is electrically noisy. Its charger, processor and USB traffic all add a little noise to its ground. Some of that noise flows around the ring as a small current. The ground in the audio cable is part of the ring, so the current becomes a small voltage on top of the audio, and that is the noise you hear.

How to Fix It
Section titled “How to Fix It”
  1. Put a USB isolator in front of your audio interface. A galvanic USB isolator passes the USB data but not the ground, which breaks the ring. Connect it between the computer and the audio interface rather than between the computer and Katla. That way it also fixes the same problem for any other gear you plug into the interface. Choose one that supports High Speed USB (480 Mbps), as many audio interfaces need it. Low-cost isolators often run only at Full Speed (12 Mbps). For example, the Topping HS02 supports High Speed.
  2. Use a DI box on Katla’s outputs. A DI box with transformers and a ground-lift switch passes the audio but not the ground connection, which also breaks the ring. Katla’s outputs are stereo, so use a two-channel DI box such as the Palmer PAN 04. A DI box outputs mic level on XLR, so connect it to your interface’s mic inputs.

If you don’t have either one at hand, these can also help:

  • Test with the laptop on battery. If the noise goes away, the charger is part of the ring. Plug the computer, Katla’s power adapter and the interface into the same power strip.
  • Unplug the Genki Link when you don’t need it. Katla plays on its own power adapter. Without a USB cable to the computer, there is no ring.