A few thoughts:
Some receivers do processing in sneaky ways. Have you tried enabling the Yamaha's "Pure Direct" mode (which disables most processing)?
Also, do you know if the Yamaha passes analog input straight through, or converts it to digital and then back to analog? Some receivers only have a digital volume, so they automatically convert all incoming analog to digital and then back again at the outputs, which introduces another two conversion stages into the audio and could potentially affect the sound.
Also the Yamaha DAC and the Exasound are different DACs, and different DACs can sound pretty different.
Yeap, I have tried turning on "Pure Direct"
I was told that the newer Yamaha receiver has no ADC for analogue multi ch inputs. Its too costly to have multiple(8 or more) ADCs. Besides, HDMI connection enables PCM processing.
You are right about the two different DACs at work and possibly deliver the differences in sound quality.
There are so many differences in the audio paths that I can't see how you can pin them on any one thing without doing some serious experimenting. And I'm not sure you can do those experiments well enough with what you have. Some possible issues.
Usb vs. hdmi
Yamaha vs e28 dac
partial analog path vs. all digital
MC decoding vs. Yamaha decoding
Volume control (even very slight volume differences will usually favor the louder option)
Differences in cables and types.
-Chris
Totally agreeable. These differences can definitely affect the outcome.
Anyway I was hopeful that someone may have gone thru' a series of test to come out with the answer. A good standalone decoder may assist in this case to dig in deeper for an answer. The decoder will have to sit in between MC19 and e28. I doubt such equipment is commercially available!
Also, unintentional listening bias. Human brains are complex beasts, and hearing is much more brain driven than mechanical.
Haha, this is complex... Perception of sound (Music) is extremely subjective.