Review on 🔌 Enhanced USB 2.0 Extender: 4-Port Hub up to 50m Over Ethernet (Cat5e/6) for PC/Microphone/Webcam – No Driver Required – Versatile OS Compatibility by Bobby Lawson

I used this to extend the USB 2 connection to my Presonus mixer with a 50ft ethernet cable. When I turn on the mixer, a high frequency (about 10 kHz) comes out of the speakers. When you unplug the extension cord, the sound disappears. I've tried powering each device from different outlets, tried using USB cables with filters (ferrite beads), tried different Ethernet cables, and even a 10ft cable, but I get a high-pitched squeak every time . When I connect the USB cable directly (moving the mixer closer to the computer) there is no noise, so this device is definitely the culprit. As an electronics engineer, my guess is that there is a DC/DC power supply in the box that uses a switching power supply and is not properly filtered. Too bad. I think I'll try to buy one of the expensive ones and hopefully it works.