I was looking for an update to my Fiio e10k for a while now. K5 Pro looks interesting, eagerly awaiting the first reviews.

I would like to see something different - I think you should lift the E10k to the next level: -dedicated desktop DAC (size doesn't matter) -keep the neutral audio character but add better components and a high-end DAC chip -keep all the connections, maybe even add optical, USB-C, Bluetooth ...

Yes, that's exactly what the rear line out is for ... connection to a different amp or powered speakers. The volume knob in the front and the bass boost switch do not affect the line out.

@HiCZoK It's likely a problem with your USB and/or chipset drivers. Perhaps search if newer ones have been released for your device and update.  

  Crosscheck with any other PC/laptop that you can get a clean signal and that it's not the Fiio. 

@Flobert Try all possible USB ports on your machine. Some PCs have incredibly noisy USB. If that doesn't help I'd suggest an active USB hub.    @Selbi EQing on the DAC-level is apparently the best way to do it because the DAC can work directly on the raw data.  I didn't use the bass boost...