[High_Q]

I have been seeing alot of graphs of THD and frequency response.  Since I favor certain DAPs because of the details and separation to offer given the right headphones, I was wondering how to check for that?  Is there any measurements for that?  If so, please provide me to some links.  I would like to see comparasons of many DAPs.  Thanks.

 

[b0dhi]

There is no direct measurement for this. The closest is probably intermodulation distortion. Possibly also spectral decay graphs.

 

[xnor]

Keep this in mind:
You probably won't notice a difference between 0.001 and 0.1% distortion but you will notice a 0.5 dB accentuation of treble frequencies (even if you cannot detect it as such). To me it seems that the latter often is mistaken as higher resolution while in fact it's just a small FR variation - which are unavoidable with some amp-headphone combinations.