flash drive or hard drive? hard drive does that when to fragmented!
NaS or Cloud?
WiFi or ethernet? ethernet better?
microwave? or tool connected to the grid?
DC on your electric cable? that clean with demanding music?
USB or Optical Spdif?
I don’t know what you mean with everything but I’ll answer to my best abilities:
- Flash drive SSD (the internal disk of the Mac Mini)
- The Mac is on ethernet but that shouldn’t impact anything bc I’m loading a downloaded file
- The electric group is shared with other devices. This may indeed be a (partial) cause I hadn’t considered yet.
- I supply AC from the Powerplant into the RME, the RME converts it to DC (I guess), I don’t use DC cables
- USB but conditioned with galvanic isolation (Intona 7455-C) and AQ Diamond USB / Curious Cable USB to connect
Couldn’t it also be the output stage of the headphone amp, or the headphones themselves?
You’ve done an exceptional job describing and troubleshooting the issue. It is curious that it is repeatable and seems isolated to a particular spot in a particular track - thus power disruptions/contamination along with HDD issues etc seem to be ruled out. I’ll be following to see what you discover.
Couldn’t the distortion be in the recording itself?
That was my thought. . . an overloaded microphone perhaps.
macmini, fusion drive?
if it’s an old Mac mini the headphone output is also a spdif Optical output?
So you have a chance to verify if it does the same thing?
Sorry for my comprehension it seems to do this on one song it’s the recording if it does this with all demanding recording then it’s mechanical!
Something is not able to keep the pace of the data transfer for the music
It happened with fusion Drive on Mac mini
It could be except that we’ve been looking at the waveform in that segment of the song and not seeing distortion in it. I posted the waveforms in this post up above. and GavinK posted an oscilloscope capture of the input to the DAC, and it, too, looks distortion free.
by the way I forgot
Depending on the amplifier you’re using
Some amplifier don’t like the 4 V output of the digital age
Back then everything was 2 v
So maybe you’re just at the limit of distortion of the input of your pre-amplification! Simple as that
Too much in volt ment! (involvement) Makes sense with the loud passage, To high(I) for your Pre-amplification input
too i input
There’s a good chance; only way to test that would be to buy a new DAC and a new headphone amp and compare. Perhaps I’ll do that someday, for now that’s a bit beyond my budget.
Thank you very much for the compliment! 
I always try to take small steps and improve as I go, slowly figuring out what does and what doesn’t work. Can’t always trust what’s being said.. I like to try it for myself and see if it works or not, so I have to be very careful not to draw a false conclusion.
Hmm well yes, it well could be. But then why would Paul McGowan list it as #1 on his playlist, if it has distortion in it? Hard for me to believe.
The particular soundwave may just be very hard to accurately convert from digital to analog.
It also happens on multiple tracks, not just this one; the Norah Jones track is just the one where the distortion is most (very) present, the other tracks are much more subtle and thus less of an issue overall.
Unfortunately I own a new M4 mac mini so there’s no SPDIF output. 
It’s mechanical for sure, there’s multiple tracks where this is an issue.
Never considered the data transfer.. I’m considering upgrading to an external SSD so I can store all my massive AIFF files there without clogging the internal SSD memory. But that just seems.. slower? in theory.
I’ll keep this in mind. Thanks for all the great pointers thus far!
Hmm well it’s an integrated headphone amp and DAC so that’s really beyond my scope, nothing I can change there. Only way to test is if I would purchase a separate DAC and separate headphone amp, then do a comparison test with RME only, RME + headphone amp, DAC + headphone amp to see.
But that would be an expensive test. Maybe some time in the future.
affordable way to test is a Fosi Zh3, cheap reliable and not bad at all!
or more cheap, Friend system! go and test there!
ok mac mini!
what the midi say?
microphone is volume down or inactive (better)
this morning, new setup windows and apple! a lot of crash about it for music rendering!