So:
Test album: "Tedeschi Trucks Bank Live - Everybody's Talking". I just downloaded it today on Tidal, so no preconceptions, and I thought it might be interesting to try this little comparison with a recording of a live gig.
DP-X1 by itself, balanced out: Great soundstage, definitely a smooth sound sig, as DAPs go; good bass, strong but not overpowering mids. Sounds like being at the gig just as much as the other two setups below.
DP-X1 balanced out > ALO 2.5mm - 2.5mm interconnect > CDM 2.5mm balanced in > CDM 2.5mm balanced headphone out: more pronounced mids. Sounds very live. Bass more focused and in your face.
DP-X1 digital out > Lavricables micro USB - OTG > CDM digital in > CDM 2.5mm balanced headphone out: smoother sound (love those tubes). Very non-fatiguing. Slightly wider soundstage.
Worth noting that the CDM's sample frequency light appears to indicate 176, despite Tidal being CD quality at best, as far as I remember. I should also mention that I had the CDM on the high gain setting (there are high and low options), as I like the extra punch, and it suited the live gig atmosphere. Switching the gain to low makes it even smoother - works well for EDM.
I'm sure this is a very niche combo for impressions but I mention it in case anyone else has the same stuff.
Pic above: DP-X1 + ALO CDM plus the necessary cables to A/B the setups described above (and yes you have to turn the Onkyo around to connect the 2.5mm interconnect to its balanced out!). The pic obviously shows the Onkyo running the IEMs by itself from its balanced output.
IEMs: Rhapsiodo Solar. Cable: Effect Audio Eros 8-braid hybrid - 2.5mm balanced connection.
I then repeated the whole thing with my Earsonics Velvets, which are a smoother, perhaps darker sound sig. The comparisons between the three setups remained the same.
Fantastic soundstage even with the DP-X1 by itself. In fact I preferred the whole setup with the Velvets, as they really convey the bass that you get at a live gig (albeit with less focus and precision than the Solars). I've avoided much talk of preference because everyone's mileage and sound signature preference varies, as we all know.
Summary: DP-X1 sound amazing balanced out, and I am delighted to have one dedicated little box to carry around that sounds so good. It is not embarrassed by adding the extra box at all. I'd be very happy using it solo all the time.
Also very happy that it pairs so well with the CDM, especially using the digital out (thank you Komstantin at Lavricables for making me the interconnect and shipping it at very short notice), which adds something extra and makes the Onkyo a great transport when pocketability is not the top priority.