Its a subjective measurement and Amir is "getting older" as he said
It also depends on what headphones he uses to listen to these, he only tested some tracks using his midrange headphones. If he was able to hear differences at all with more detailed tracks, this means that people with better headphones (lower distortion) or using additionally detailed tracks and/or possibly younger with better ears (please keep in mind that younger doesn't mean better ears) will be able to tell the difference more easily.
The increase in output impedance means that low impedance headphones will suffer one way or the other.
So please do not take Amir's subjective impressions under his mild testing as being more important than the objective tests that this unit UTTERLY FAILED.
Products like the DX7 and DX3Pro are available around the same price and offer awesome performance.
Nevermind that products even like the March Audio DAC, that while more expensive offer performance that is many times in excess of this product for around the same price.
For the "lower price" you could buy the ODAC or D10 or D30 + JDS Atom Amp and have performance that no Audio-GD product could touch.