not all digital sources are created equal. That's why vendors go to great lengths , dealing mainly with the power section, then IIS to SPDIF or USB output conversion, etc to arrive at digital outputs as pure and jitter-less as possible . Even digital top transports like Auralics Aries may not necessarily reach top CD transports. I have done experiments comparing tablet PC and desktop PC with USB(direct tap in or through external linear or battery powered USB hub or optical output to Hugo and Audio GD 10SE then output to Hifiman RE 262, and also further down the chain to 400w into 4ohm high resolution high current power amps to HE 6. The results could be grossly different.
I read many post here which says so long as there is optical or coaxial out from the dap, the results will be the same.I do not believe it. Maybe the present totl daps concentrate on the DACs and amp inside and that the implementation for digital output are more or less in the same rank. I still believe there may be differences between Fiio X5, HM901 and AK 240 and I 'd like to hear comparison from you guys. Some even say that there is no difference from the digital output from Iphone!
I believe how much you can hear a difference depends on the calibre of your gears down the stream. For example, using power amp to HE I can discern huge difference between various methods of USB output and SPDIF output , and the difference in calibre between Audio Gd 10SE(which is itself a very capable DAC/Amp , can perfectly drive HE-6 and is a steal at its price) and Hugo, such difference may not be so apparent when attaching RE 262 to the two DAC/amps. With HE -6 driven by the power amp, the two DAC/amps are simply not in the same league, in so far as resolution, punch, airiness and musicality is concerned, especially when it comes to old , non-audiophile , 44.1 recordings. I'd like to hear someone comparing Master 7 and Hugo as a DAC.
Any way , to put it simply, different digital outputs varies gravely. For this purpose I am waiting for QLS 360 dap. The vendor goes to great lengths as if doing totl desktop or hifi rig digital transport ,to make sure the power supply as good as possible within the physical limits of the dap, accounting for 50-60% of the cost and space, and write proprietary computer code for single thread handling of all IIS to coaxial/optical conversion. The end results ?- the dap itself may not match HM 901 or AK 240, because it's not using dual totl chips and class A headphone amp output like Hugo. I'd , however, expect it's coaxial or optical output to surpass even AK 240 and HM 901( it even output Dop at coaxial and optical ouput !)
We'll see .