So now I could definitely and confidently confirm that player changed it sound signature after I upgraded from 1.0.4 to 1.0.6 firmware.
In 1.0.6 sound is brighter - and it is totally unacceptable for me. I just have a pain in my ears from this sound. It is too piercing for me.
I have tried to fix it with EQ - but it did not helped (overall quality was not good).
So I have found 2 methods - how to make old sound (preferable to me) back.
It is bad that if I will stick with 1.0.4 firmware I will be not able to get fixes for bugs, but it is anyway much better for me than have brighter sound signature.
Also if I will rely on some person from internet who applied his fix on top of Fiio firmware - I will be not able to be sure that he will not hacked my device in some way (as he is not official developer from Fiio company).
I want to share my experience on how to bring back old sound in case if you liked it more. In case if some other forum readers have similar issues with brighter sound signature:
Fix Fiio X7 mark 2 too bright sound signature guide (after upgrading from 1.0.4 firmware):
1st way - downgrade player to 1.0.4 firmware:
1) Download 1.0.3 firmware loader
http://fiio-firmware.fiio.net/X7MKII Firmware Upgrade Tool with FW1.0.3.zip
2) Follow instructions from this Fiio page to install 1.0.3 firmware to your device
http://fiio.net:8000/forum.php?mod=viewthread&tid=41890
3) Upgrade device with over the air update from 1.0.3 to 1.0.4
Attention - your data inside player storage will be deleted - so make sure you copied all your music to flash card!
2nd way - use some custom firmware that fixes the issue in 1.0.6:
1) Download and install modded firmware that fixes issue with bright signature
Example of such firmware and instructions how to install it could be found here:
http://www.fidelizer-audio.com/fiio...6-released-with-bright-sound-signature-fixed/
@FiiO
Is there a plans to restore old sound signature (like it was in 1.0.4) in new 1.0.7 firmware?
Or in case if this is not possible: I think the best way to satisfy both kinds of users (users who like brighter sound and users who like warm sound) is to release 2 variations of the same firmware.
One with brighter sound. And second with more warm sound. So in this way I will have both - fixed bugs and warm signature that I bought from store and liked.
FYI
@gazzington