As promised today I tested
Absolutely could not conclude any background sounds/noise such as your examples.
I tested only with MP4 files
You say :
Yes, always at the same points. We may think that these videoclips are just "broken" (I don't belive) and there is nothing we can do with it. But why I can't hear anything wrong when as a source I use laptop, Blu-ray, DVD, other satellite receiver (apart from Duo2), etc?
I doubt that the problem has anything to do with HW problem
It is practically impossible if the problem is hardware that you have a
always at the same points.
Yes. I have a lot of downloaded videoclips from youtube. Some of them are free of any noise, some are more or less noisy, if you know what I mean.
It may depends on the tone or frequency of sound - I think.
Does it mean that Duo2 is more "sensitive" and I can hear something what I can not hear on different device?
Again proof that it is not a hardware (some free some noisy.)
Is software ? possible
Perhaps files on one device producte and the other does not produce strange effects because of differences in software .
However, this is unlikely since you say that this problem is not present in all files.
I think that is a good direction
to estimate why in some files you have noise in others you do not have.
On the other hand testing from other people , noise have not been confirmed.
Also not my test for the third time in the last few months it has not confirmed.
I used also the test mp4 files from the net
in quieter parts I not heard absolutely nothing.
Try to test with this mp4
My Other test files are too large to upload.
I wonder, result ??
I think it is not fair to make such a campaign abt the box and VU+ for which yourself do not know what the problem is,and which is the cause.
One thing is absolutely certain that it is not hardware.With your description of the problem it is almost impossible.