Thanks for your patience as we sort this out!
I’ve done an in-depth analysis of the Def Leppard song and the effect of the Paris profile. Using the MBox as a DAC I am not hearing any distortion that is not already present in the original recording. However, it is possible the distortion you hear is related to some software/hardware issue. Since I cannot reproduce that, I will address the distortion as I hear it.
Take a look at the audio in Adobe Audacity:
This is the original audio as it transitions from song 3 to song 4 of Songs from the Sparkle Lounge (I managed to find the flac version just to be sure). There is a LOT of distortion all over this album though I don’t hold that against the engineers because that is used all the time for effect. If you look very carefully at the right half of the image you can see clipping artifacts in the spectragram (that is the orange display below the green waveform). You can see very faint vertical lines in the black area above the lower frequencies of the big power chord that starts the song. Look at the area between 11:04 and 11:08 according to the timeline at the top of the image.
Here is the same passage with the Paris profile applied:
I am using Soundflower to record from VLC back into Audacity. You can see the waveform is about 3dB lower due to headroom built into DPS Reflector so you can see there are no clipped samples due to DPS processing. Take notice of the vertical lines in the power chord section. They are much brighter! Basically, the Paris profile is amplifying these very quiet elements and making them much more audible. That translates (to my ears) as a crackle laid over the power chord. Paris is a fairly aggressive profile that seeks to bring out all high frequency details for those speakers or headphones that need this kind of help. Perhaps a less aggressive profile would be better for you to try?
And, to be super sure, I have added Paris -3dB profiles to Dropbox. Give these a shot and let me know if these profiles have any effect on what you hear.
If the distortion you hear is more obvious that what I am describing, I will need to hear what you hear. Distortion can have many different causes and I can usually pinpoint the cause if I have the opportunity to hear the issue. You could even record the output from your DAC and some decent speakers with an iPhone and I should be able to discern the cause. You can email an mp3 to email@example.com or send me a dropbox link.