iFi iDefender+ Ground Loop Eliminator

Stop USB Ground-Loop Hum at the Source

The iFi iDefender+ is a compact inline USB accessory designed to address one specific but frustrating problem: audible hum or buzz caused by a ground loop between a computer and a USB-connected audio component. When it detects multiple ground paths, the iDefender+ interrupts the computer-side ground while maintaining the USB data connection. This can remove the unwanted loop without requiring changes to the safety grounding of the rest of the audio system.

Ground-loop noise often appears after a computer, powered DAC, amplifier, active speakers, or other grounded component is added to a system. The result may be a steady low-frequency hum, buzzing that changes with computer activity, or noise that disappears when one cable is disconnected. The iDefender+ is intended for that situation; it is not a general-purpose tone control or a repair for defective equipment.

Optional External Power for Bus-Powered DACs

If the connected DAC normally receives power from the computer's USB port, connect a suitable low-noise 5-volt supply to the iDefender+'s USB-C power input. The accessory then blocks the computer's USB power and substitutes the external supply while leaving the data path intact. A self-powered DAC normally does not need this additional connection. Maximum supported external power is 5V/1A, and the unit is not intended for USB Power Delivery charging.

Who Is This In-Line Filter Best For?

• Listeners who hear hum or buzz after connecting a computer to a USB DAC.
• Desktop-audio systems using powered speakers, headphone amplifiers, or grounded components.
• Music servers and computers sharing power or signal grounds with a hi-fi system.
• Bus-powered DAC owners who want to substitute a clean external 5V supply.
• Installers troubleshooting a confirmed USB ground loop.

It is less likely to help with hiss from amplifier gain, mechanical transformer hum, damaged cables, wireless interference, or noise that remains when the USB cable is removed. Diagnose the source before changing connections.

How (and Where) Does It Connect to Your System?

1. Power down or mute the audio system.
2. Insert the iDefender+'s male USB connector into the computer, server, or source USB port.
3. Connect the existing USB audio cable to the female USB socket on the iDefender+.
4. Connect the other end of that cable to the DAC or USB audio device.
5. For a bus-powered DAC, attach an appropriate 5V supply to the side USB-C power input.
6. Restore power and compare the system with the filter installed.

The listing shown is the USB-A version. iFi also manufactures other connector arrangements, so verify the source port and cable before ordering. USB 3.0 operation is supported and the device is backward-compatible with USB 2.0.

Frequently Asked Questions

Will it improve every USB audio system?

No. Its primary purpose is eliminating a USB ground loop and optionally replacing noisy computer power. A system without either problem may show little or no change.

Does it disconnect the USB data signal?

No. USB data continues between the source and DAC; the device changes the grounding and, when external power is used, the power arrangement.

Do I need an external power supply?

Usually not with a self-powered DAC. A bus-powered DAC may require a compatible 5V supply connected to the iDefender+.

Can I use a USB-C Power Delivery charger?

No. Use a suitable standard 5V supply within the 1A maximum rating rather than a USB-PD arrangement.

Is it safe to remove the AC safety ground from my amplifier?

No. Never defeat a component's protective-earth connection. The iDefender+ is designed to work in the USB signal path without altering equipment safety grounding.