I believe I answered that when I said "Too much information overload" Its the wrong pairing with the N3U so big thumbs down.
The DTE900 is aggressive in the upper mids and treble so the N3U really reveals all the information in a even more forward manner especially in Tube mode.
The M5U with its warmer signature balances the upper mids by taming them down a bit and smooths out the entire playback. Big thumbs up with the DTE900
On the other side of the coin the Myer-Audio CKLVX D41 and the Shanling ME600 are surreal on the N3 Ultra, with super revealing DAP'S you need to be mindful of your chain.
I certainly don't think there is any hard and fast rule, all our ears are different as is our tastes. It a subjective hobby.