Sound via laptop vs phone vs tablet

There is quite bit of confusion here. The format of the stream is irrelevant, because you are using the same stream in all three cases. However, you are using the analogue output of the three devices, and they each have a different inbuilt DAC. The snag is that by and large none of such devices have a decent DAC - the environment is just too noisy. See here for some measurements: http://archimago.blogspot.nl/search?q=laptop
Even a dirt cheap usb DAC like the Behringer UCA 202 will be a vast improvement. See e.g. http://nwavguy.blogspot.nl/2011/02/behringer-uca202-review.html

@willemj  you misread the post. He is getting digital out of his phone by using USB on the go. Should be all the same data stream. Perhaps more jitter? 

@crwindy  let us know if that app helps you. I take Digital  from my iPhone and iPad by running  lightening out through apple camera conversion USB adapter and then  through a powered hub. Does not sound bad, but have not compared it to a PC source. 

OK, my misunderstanding. And that should indeed all produce the same datastream, and bits are bits, so there cannot be any difference (are you not imagining things - the audiophile curse?). Unless of course the datastream is somehow compromised by the settings in the devices. Jitter really has to be absolutely awful to be audible.

USB Audio Player Pro does not support Spotify. I just use the computer.