I've gotten into headphones recently and acquired a Dragonfly Red. Feeling guilty over not getting an i-something I decided to get an iSilencer to go with it. The whole usb thing is frustrating in my experience, as there's so much variability. The iSilencer turned out to be no exception, albeit with some positive results.
Since the iSilencer is designed for usb3 I started with that. I attached it to the DFR and plugged them into my PC. The headphones are Sennheiser 599s. There was an immediate reduction in noise and mids smoothed out even more. Very easy to notice. However, the treble sounded harder and overall there was a dryer, less organic presentation to the music. I think objectively some would say it was better and odds are it is highlighting the inherent flaws of my pc, but still, it didn’t feel right to me.
For kicks I swapped the combo out of the usb 3 slot and into a usb 2 slot. Sound quality worsened. Not a good match. Then I removed the iSilencer and listened through the USB 3 port. Hm, not as clean and the treble hardness was still there. Finally, I swapped back to the usb 2 port, again no iSilencer. This was the original slot before I ordered the iSilencer. Voila. The music returned to the organic, beguiling flow I’d been listening to the past few weeks. Weird. But this has happened with me before. For some reason some usb slots tend to sound a little better than others, and the usb 3 slot can have a cleaner but drier presentation. But all this is a reminder to me though of why I abandoned usb for my main 2 channel setup for an Ethernet based solution. USB is just too dang finicky. The iSilencer works as advertised and is not at fault. I highly recommend it given its cost.