Back in the mid 1970s humankind found out that measuring audio circuits doesn't reveal or explain the audible sonic differences perceived by the human ears.
I am amazed that some can't hear the difference between the digital out (pure therefore the reference) and the analog (two additional conversions, unpure?) no matter what convertors are used. I can only conclude the listener is using very distorted "amplifier/speaker rigs".
As I've stated here previously and still my experiece:
With a clean amplifier/speaker rig - the digital out to the DAW recording software being the reference:
When comparing this reference digital out recording to the analog out recording there is audible degradation applied to the analog output recording that is blaringly obvious.
The analog out (dual converted) track has an addition of raspy hash or harshness (distortion) added to the upper mid/high end or put another way, lacking of clarity or purity that is there in the reference digital recording.
I also completely understand that many people using the KPA don't hear, don't care, use it in a different type of application or have to use the analog outputs.
I had to use the analog outs up until the 48k was added.