I'm hoping someone can explain what I'm experiencing with two different DAP's, as it doesn't make any logical sense to me. There's obviously some process in the chain I'm not familiar with, so I'm hoping for some education here. I've been listening to music for a few months using a DAP outputted via USB to a DAC, then a line out to an AMP. The specifics are Shanling M0 (DAP) > ifi nano BL via usb (DAC) > Cayin C5 via 3.5mm line out (AMP). This combination sounds fantastic, but my DAP (Shanling M0) crashes a lot, and I was looking for a better overall user interface. I purchased a fiio M6 and started comparing the UI and everything else. At the end of my comparisons I plugged in the M6 into my normal chain (m6 > ifi nano bl > cayin C5), and was surprised & confused when the sound quality was different from what I was used to. I went back and forth between the Shanling M0 and Fiio M6 several times, and on several different days, and each time I heard an obvious difference in the sound quality. The Shanling M0 as the DAP has more details but a thinner sound, whereas the M6 has a fuller sound with more bass and much less detail. This makes no sense to me as I thought the DAP is just transferring a standard format digitally over USB to the DAC, so I wouldn't expect there to be any sound change between two different source DAPs. So, if the DAC, Amp, and cables are all identical in the chain, how is it possible to have ANY difference on the final sound? Are different DAP's sending different data over USB to a DAC?