Re: [LAU] USB cable with ferrite core

1) Perhaps it is not so much the issue of whether the cable has a ferrite RFI suppressor but the quality of the cable that is important.

I recommend that you use a quality USB 2.0 spec'd cable. Better yet, use a USB 3.0 cable.

2) Unfortunately, USB is inherently noisy. Using a ferrite to reduce common-mode currents in the cable is, in principle, a good idea. However, there are potential issues. Either or both the sound card and your computer's USB port may not properly isolate the signal and power grounds, and there may then be noise issues if the two grounds are not electrically the same. When you install a common mode choke (the ferrite), you are effectively isolating the two grounds. This should be fine, but if either sound card or USB port are not properly engineered, there could be a problem. You could try running a wire (16 gauge or larger) from the chassis of the sound card to the chassis of the computer. Do not put a ferrite around this ground wire.

3) Another potential issue is the sound card power supply. Unfortunately, almost all power packs sold these days in the U.S. are Chinese switching power supplies which produce TREMENDOUS RFI. You could try a linear power supply instead, although they are getting harder and harder to find.