Hello JosephMorin as proof that the sound change, with the new firware; do you have two AR-M2 with different firmware to test and notice the differences? ... Regards...

Dear Hawaiibadboy or those who can answer me, someone has tried with this new firmware 2.6.3 the flac files that I did not recognize them with the previous firmware 2.5.6, (some flac among other formats); and the other query this 2.6.3 firmware has search system, thanks for your answers :).