Hi, I just now registered to this forum even though I read a lot about the mx1 here. I'd like to share some impressions on my audinst:
It sounded good straight out of the box, but restless as I am, I had to change/add some things. At first I noticed that the analog part of the wm8740 is powered via USB. Thats very bad, because the USB power usually has a lot of ripple. To solve this I put a ADuM4160 and a regulated 5V PSU in the USB line. Next I swapped the DAC output opamp for a pair of OPA827s. Then I did the same with the line out buffer, because I mainly use the line out. Finally I swapped the opamp caps for Silmics, because I didn't trust the Sam Youngs.
Here is a photo of the result:
Was it worth it? Yes. The ADuM4160 enhances clarity and reduces some sqeeling noises from the computer's PSU. The new DAC out OPA827s enhance the sound in every aspect: dynamics, precision, linearity, soundstage, ... The new line out buffer OPA827s haven't got the HF harshness of the original OPA2134 and add even more soundstage and precision. With the new caps the sound gets cleaner and has a much better dynamic range.
PS: I use the original external PSU from Audinst. I don't think a better PSU would enhance the sound quality, but I will try when i get a chance.
@borez: I tried the OPA2227. It sounds much better than the LME, but won't give it much more warmth. I had the OPA2227P and it worked fine. There is a sonic difference between the HP and the RCA out. The headphone out has more bass.