When I moved house and setup up my guitar and synth bits in the new place, I was treated to the most horrendous ground hum, staticy, zuzzing noise through the monitor speakers from the USB audio interface attached to my desktop DAW system. I never had this problem at the old place aside from a very small hum which a small Behringer Hum Destroyer/Suppressor fixed.This little iDefender fella removed most of the noise, leaving only a very faint electrical connection sound in the distance if you put your ear to the speaker and which you'd easily forget about when audio was coming through. So, it did the job it was supposed to do but it is quite expensive at £60.The reason I say "check you really need it" is because I did little more investigation and found a better and cheaper solution for my setup. As I had never had a real problem before, my Steinberg audio interface had always been connected to the Mackie monitors via mono 1/4" cables. Apparently, these are called Unbalanced. The Steinberg and the Mackies both support TRS (stereo) cables otherwise known as Balanced. No idea what all that means but professional stuff all generally supports Balanced. I bought a pair of TRS audio cables from Amazon (RUXELY 6.35mm TRS Instrument Cable) for a grand total of £12 and voilà. ALL the noise vanished. Nothing evident even with your ear up against the speaker. Didn't even need the Behringer.Problem solved. iDefender not required. iDefender returned. Balanced is clearly the way to go and I probably should have known this but I'd never had this problem before in the previous 15 years with all sorts of kit and different interfaces. Balanced TRS cables on everything from now on. That said, if that doesn't do it in your situation then the iDefender will likely get the job done.