Ground loop and interference with USB audio devices

How does ground loop sound like

With ground loop (DAC connected straight to the PC):

Without ground loop (A2circuits isoUSB+ installed):

Digital ground loop noise

This kind of higher frequency hiss is strictly related to digital source of the ground loop and popular solutions like common power outlet could not solve the issue.

Another solution that is strictly unrecommended is to lift your protective earth pin. This exposes yourself to the risk of electrical shock in case of accidental short of the high voltage to the chassis.

Thus, using an USB isolator is a recommended solution, as ground pin remains connected and protective earth can ground the chassis etc. Additionally, it provides 1500 V or more of the isolation voltage that can help you in case of electrical failure or surges.

Before and after ground isolation

Following plot denotes the noise spectrum before installing the USB isolator onto audio interface (blue color) and after (yellow color).

Over the 80 kHz frequency range measured, you can see there up to 32 dB noise reduction and hear only natural noise that is always present.

Keep in mind that for audio interfaces, a High Speed isolator that supports 480 Mbps is required. Most of cheap isolators support only 12 Mbps USB Full Speed.

Interested?

Visit our offer on Allegro store:

Or contact us for other possible payment or delivery method via contact@a2circuits.com. Any questions are welcome as well.