I don't want to do it. Below is a long explanation.
I don't like any kind of software processing. In hardware, I don't like equalizers and other "beautifizers". I prefer bit perfect playback of digital content, when the quality of the sound mostly depend on the hardware. This way, an ultimate recording sounds ultimate, a good recording sounds good, a bad recording sounds bad.
I never tried the original 2.0.0 firmware. I've flashed 2.0.5 as the frist step after unboxing. Then I ran a test to check if DX90 is bit perfect, which succeeded. Same with 2.1.0.
The test is quite simple, I use it over past 10 years with sound cards, and I wonder why other people don't use it. I connected DX90 S/PDIF to my pre-pro (Onkyo PR SC-5509), and played back a flac track from a DTS Audio CD rip. The processor has detected DTS stream and has decoded it into 5.1 sound. But only if EQ is turned off. Because DX90 software treats DTS-encoded stream as a usual PCM sound data, it would alter it the same way as any other music records, if it alters sound bit stream either way. But the fact that the processor decodes DTS stream flawlessly, exactly means that DX90 player outputs sound stream unaltered, if EQ is turned off. This is called bit perfect playback
Now you might wonder what if the player has two different, parallel, paths for output to DAC and to S/PDIF... I'm sure it hasn't. To confirm that, I even looked into MangoPlayer in a disassembler (IDA).
Now, bearing in mind that both 2.0.5 and 2.1.0 are bit perfect, what is the difference between them? There are two:
- Changes in MangoPlayer to fix playback order of files and tracks in CUE sheet (that's what I asked them for ).
- Removed 5 libraries from system/lib/soundfx.
The #2 is the most questionable change. Well, probably I have to tell you that I'm professional programmer for past almost 30 years, involved into mobile and embedded platforms since 1995, and for past 4 years Android is one of the platforms I work with. That's to avoid speculations about my experience.
The soundfx filters are not used by MangoPlayer. They can be used only by Android sound path, but MangoPlayer does not use Android sound path. I've read Android programmer's documentation on those filters, and I'm pretty sure they are not used. Moreover, with 2.0.5, I tried to delete the core Android sound files, and it changed nothing: MangoPlayer continued working.
So why iBasso decided to delete them? In my opinion, to stop speculations floating around.
Why somebody hear different "sound signatures" of different firmware versions? It is up to them. I do understand that there are different "sound signatures" depending on temperature, humidity, time of the day, day of the week, mood, tiredness, how good/bad IEMs inserted etc. etc.etc. That's why I said in comments to "my" firmware that it
may change the "sound signature".
But hey, all in all, even it is truly confirmed that soundfx files being present, even not used, affect the sound signature, for me it's exactly mean they must be deleted and never put back! Because I like bit perfect sound!
If you like to listen not to music but to distortions, wait for RockBox to appear, and you'll have them all
Frankly, when I was waiting for my DX90, I've read a lot of forums, built RockBox for Android myself to try, had read its sources and decided that this is not the way to go with players like DX90. At least - not for me.
By the way: apart for specific test tracks, I didn't listen lossy files of even CD rips on DX90 so far, only hi-res records. That's what I purchased it for.