It took me ages to get used to the Mojo.
At first I found it hollow, cold, and thin, however more detailed than my other DAC. Since it was more detailed I persisted with it for a while suspecting some burn-in. (Or brain burn in which some suggest.)
After about ten days I noticed it seemed very smooth, because there were no rough hiccups from poor quality conversion. After that uphill moment, it continued being all uphill. I adjusted or it adjusted and it was all that everyone says it is.
Yes, exactly like you wrote "hollow, cold, and thin".
But, I believe in break-in. I did a lot of tweaks with my tube amplifiers and I built from scratch my tube phonostage.
I can say, that even brand new cathode resistors (are shunted by capacitors) sound horrible during breck-in period.
I listen Mojo in my system with 300B amplifier and Altec 604E speakers.
I also listened Mojo with Audeze LCD2F.
I think you're on the right path so to speak. As time went on the Mojo just got better everyday for me.
The hollowness I experienced turned into incredible sound-staging on my desktop speakers, (which are Q Acoustics BT3). My old DAC was a warm, thick, (and almost fluffy sounding) Meridian Explorer (ME). It's a good enough DAC at its own price point, but I knew I wanted more. The Mojo is much deeper in the soundstage on speakers, and that was what I was hearing as hollow. The Mojo also fills out the sides of the soundstage with equal details as anywhere else.
Whether or nor burn in of the Mojo took place, Rob Watts says no. He says it's brain burn in. I think brain burn-in really happened for me because there was a substantial difference between the Mojo and ME. However we always hear about hardware needing time. When I eventually came to terms with how much better the Mojo is though, I realised it took time.
To me the Mojo no longer sounds thin. It's just that the details and effects on sounds are more spaced out. Whereas the Meridian Explorer left everything flatter in soundstage back to front. (To me the Mojo now today, sounds full and solid.)
It took me about ten days of lots of listening before I began to feel the Mojo was smooth. This was due to detail and it never going out of tune or harsh. That's a lot of running time. Fast forward a few more weeks and I accepted the Mojo.
There is also a really important aspect that giving the Mojo bit-perfect files makes a real improvement too. This I discovered a few weeks in with the Mojo because I was reading this thread. I bought JRiver so I could access bit-perfect files. This improved warmth and timbre: well everything really.
Fast forward again a few more weeks and I was felt the Mojo was worth its price, just. It was sounding analogue and a beautifully comfortable warm, and smooth. A few weeks after that and I felt the Mojo was part of my life. Now I don't know if I could live without one. (If you can imagine going back to an ME after getting used to the Mojo.)
As it says at the end of the What Hi-Fi review of the Chord Hugo. "You'll wonder how you ever managed without one."