I've tried all of the "combinations" described above and couldn't reproduce the problem. I'm running x26pro with foobar2000(1.6.6), Win10 Pro, ASIO through USB. Tried all of .dsf(DSD), .flac, wav, .iso and everything is playing flawlessly and no hiss or noise of what so ever when turning off/on DAC with or without input cables. I never have DSD on DAC's display whenever turning it on. Always says PCM when turned on. While, when playing DSD files it states DSD (for, example: DSD 2.82MHz)
I'm running a proper tower PC. I've also tried to run USB output on a Macbook pro and no noise either. Although, only was able to play DSD files by means of DoP. In windows It's also possible to output all of system's sound through x26pro (though it'll go through Windows' sound system and wouldn't be bit perfect as in Foobar2000, but for watching movies it doesn't matter)
Try checking you USB output hardware and then also the correctness of installed drivers and plugins in foobar2000. I believe other players also need some plug-ins to work with DSD files. I just like foobar2000 most of all.