
In the 1.2.3 firmware they were actually handling the voltage to the Sabre DAC slightly different, so the SQ suffered. Try downloading and applying that update (totally reversible), then listen for the bass to come all lose and sloppy 
Oh and when I say "all lose and sloppy", it's still better than most DAP's out there, but not very good by DX100 standards.
Fart-incontinence but for a DAP
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So no flaws. :P