You said previously, if you unplug the usb from computer to DAC, there is no noise on the DAC. Therefore, the DAC is not the problem, it's the usb connection from the computer to DAC causing this ground-loop noise issue. The DAC is not the problem.The noise comes directly from the dac itself. Read my replies
I do not have an optical port on the motherboard. I had no idea usb to Toslink adapters were a thing, this sounds optimal if the iSilencer+ does not work
As suggested before, either go with balanced cables or Simply get the usb to toslink converter.