After we moved to a new home, I had not been able to record vocals on my computer due to a constant electronic noise in the background, something like a high-pitched whine and chatter.
After a lot of troubleshooting, I purchased a Ziocom Ground Loop Noise Isolator from Amazon ($9). It is a small non-powered device that plugs into the microphone input (3.5mm) on the computer, and the output from the mixer board plugs into the ground loop isolator. Just that quickly, all the chatter stopped and the recordings are clear again, except for a background hiss. I’m going to try a DAC to convert to USB digital prior to the PC and see if that fixes it.
The concept is that the ground point of my computer and the ground point of the mixer board are different, even though they are in the same room. This creates a slight “potential” (DC current) which is then amplified by the mixer as electronic noise. This gizmo filters out that current and lets the audio signal through.
I used an XLR female to 3.5mm audio cable from the mixer to the isolator.