I had somewhat similar problem with my previous usb dac (Nuforce udac2 = garbage). I then learned that any dac (or audiosource for that matter) should have a separate power, not usb powered, because it creates lots of interference. Now I have real dac with separate power and balanced xlr in-/outputs (Dspeaker Antimode DaulCore) and barely hear any buzzing even if I put my ear right at the driver.