First of all I want to say that I've also found the Dolby upmixer to sound the best. But I've not bothered to in depth compare them.
Let's not forget all the times the sound on the actual disc is wrong as well! I've personally experienced this where I had to send in my disc to Paramount and they sent me an updated disc. The dialog was mixed in the center channel + the right channel or something like that. A lot of movies just have really poor mixes as well and once you find a good mix you'll be lucky if it's not brick-walled at 30Hz..or has a lot of clipping or something.
There are many variables here but yes history tells us that there is a reasonable chance that Arcam messed something up. But it's like this with ALL AVRs.
Until someone can compare a known good DTS soundtrack with a known working AVR it's had to say what the issue is that people are experiencing. I might have a listen to some older DTS tracks if I have time..People who have the time and energy maybe you could tests some other discs as well to see if it's consistent.
Room| Treated | Sound| Front: Ino Audio i32s, Center: Ino Audio i16s, Surrounds: 6 x Ino a2, 6 x Ino a1, Subs: 6 x Ino Infra-Y|
Picture | Epson TW9300, Seymour Center Stage UF 130.4" retractable 2.35:1 |
Electronics | Arcam AVR390(Dirac Live), 3x Ncore nc400 monoblocks, Emotiva XPA-2 Gen2, EP4000, Panasonic UB700, Allo Katana + Isolator 1.2(Roon bridge/DAC), ATV 4K |