How are you hearing no difference?

Funny that this was mentioned. The hearing in my left ear is worse than my right. As I was learning about speaker position and listening position etc I cupped my hand behind my left ear and it made a big difference in the size and shape of the sound stage. But it did have a hollow 'sea-shell' quality to it so I tried different hand shapes and was able to eliminate that.

I'm glad no one saw me doing this...my wife already has plenty of reasons to have me committed. 

Anyway, this worked but is very impractical. Also, with a little more time and effort I was able to balance things out with minor adjustments to speaker and listening chair placement. So now I appear semi-sane while listening.

The cupped-hands technique definitely yields a "sea-shell" effect.
Closing the eyes always improves aural acuity.
Removing eye-glasses does too.
Still trying to prove to my wife I'm semi-sane also...

Act chew ally the cupped hands improves dynamic range, especially for systems that lack dynamic range, and loudness, i.e., a better antenna, but the down side is it impacts soundstage. Once your system can perform dynamically, e.g., room acoustics treatments, you’ll discover the cupped hands doesn’t do much at all. Recordings are made with human ears in mind, not Mr. Spock’s. You’re not hearing the rear reflections since the hands block them.

In fact, in the case of power amplifiers as an example; it needs to accurately amplify the input signal, and transfer that signal, fully intact, to a low impedance load.
A well-designed power amplifier, in theory, is not supposed to reshape the input in any unintended or involuntary manner, so I support the concept that accuracy improves when the potential for error and distortion is minimized. 

Hence there are indeed, subjective differences in DAC,s and particularly pre/ power amps - however: much depends on how they integrate with the speaker load and the components having low errors and distortion.
see: https://www.thesoundadvocate.com/2018/10/the-role-of-power-amplifiers-today/

Unfortunately, there are many people who’ve never been taught how to listen or what to listen for and that’s because they’ve never met a person, or found a dealer/store, who was willing or able to teach them.  Can you tell the difference between a male and female voice?  Congratulations, you can hear.  If you go to a Hifi shop to listen with the preconceived notion you won’t hear any differences, then there’s a great chance you won’t.  The teacher has to be willing to teach, but the student also has to be willing to learn...