Thanks. I've read so many responses that say they could tell the difference, it made it more difficult for me to decide between the SR7012 and X4400. In the end I chose the X4400 because it seemed like a great value, and I kind of suspected what you shared could be the case.
I understand the dilemma, been there myself. It took years before I decided to read subjective reviews for fun only, except on reliability issues and/or obvious sound quality related issues that are reported by a large number of people online, relatively speaking. For example, if 10% of 50 reviews described the same or similar issues, then I may take it seriously. The claim that Yamaha AVRs in general seem more reliable could be one such example. Other than that, subjective reviews on sound quality related things tend to exaggerated, embellished, and are prone to expectation bias, influenced by hearsay from the old days etc etc..
Now, if you look at it logically, those who claim M has a warmer sound than D and D has a warmer sound then Y in general are just claims based on users subjective impressions in their own environment using their own combination of gear and media source, and nothing else really. On the other hand, those who claim there are no brand sound signature are also based on their own subjective impressions in their own environment, gear combination etc. as well, but their claims (such as mine) do have facts and figures, albeit not complete on their side. That is:
a) design (say, comparing the same class such as AB amps),
b) the use of same or similar components, example: comparing the AVR-X4400H to SR7012,
c) bench test results that support the advertised audio related specs
d) the fact that distortions, such as THD+N <0.1% is widely accepted as not discernible by normal people
Narrow that down to D, and M, the only logical reason for the M to sound different is the HDAM modules. Take a look of the official Marantz blurbs on them:
https://www.acehomeaudio.com/single-post/2017/10/14/What-is-HDAM-and-why-does-it-matter
Doesn't that look like something written by their marketing department? The fact is, those modules as shown in the schematics, appeared to be used as a final buffer stage for the pre-outs only. Even if they do outperform OPA/ICs, they won't make a difference because if you believe they are the best in the chain then they are limited by the bottleneck components such as other OPAs/ICs upstream, as Dr. Rich (a PhD in EE) suggested in a hometheaterhifi.com article that I linked in another thread. Also, clearly their design goal is still just to achieve as much transparency as possible, not to "tone" the sound to the often claimed "warm" side as such.
So, believe in marketing hypes, hearsay, or incomplete facts and figures, tough choice indeed but is your choice in the end. For me, I have the Denon in the HT set up now for a 3 months already and I don't miss the $3000 Marantz AVP at all. I do love the AVP and will keep it in my two channel system unless someone offers me at least $1000 for it.
