After changing the setting, the audio improved a bit but not much. It started clear then noise, then clear and noise. I am starting to wonder if this is a buffering issue, so I also enabled large buffer. No improvement.
Could be related to the DSD files… Were these extracted from SACD .ISO?
Make sure your DAC is at the top of your USB Device Tree hierarchy… Distortion is different from interrupts or stuttering, which would be due to data latency… The DAC should always be the first device if your HDD is on the USB bus… If you have Thunderbolt or Firewire, move you HDD to that bus… Obviously, the transfer speed of the HDD is always something to consider… However, it boils down to the bus bandwidth and the transfer speed of the storage device.