ibasso D4 vs. D6

iBasso D4, $199, D6, $275 purchased from iBasso

iBasso D4 - Potentiometer a little "squeaky", makes a mechanical echo noise on turn on, as if something is vibrating inside the case.  Gain and Battery / USB switch throw too long and feel cheap.  Slightly thinner case than D6.  Larger soundstage, more air, blacker background than D6.  Non rechargeable 9V battery

iBasso D6 - Silver, still deciding if I like the silver, I ordered in black and silver arrived.  Switches more solid feeling than the D4.  Potentiometer quiet on turn on, Gain and Battery / USB switches quiet.  On first listen, D4 sounds more powerful with more air than D6.  Smaller soundstage than D4, more intimate sounding.  More analytic sounding than D4 and a little "brittle" sounding.

Tested with Beyer Dynamic DT770 Edition 250 ohm