Nope I updated it one time when I owned it. Didn't notice any changes in sound at that time. Still sounded rather harsh in the highs for me and the bass was bloated. With usage it did calm down a little but still was muddy and harsh for me. I was just glad to sell it off in the end. Was not very happy coming from the DX100 at that point
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Regarding the SD Cards well that's just what I hear. I'm not gonna purposely inconvenience myself if I didn't hear an appreciable difference. That really makes me wonder though what that one guys posted earlier on (the read speeds of the 32 GB cards being faster than the 64 GB cards?). Whatever it is I didn't like what I heard when comparing them. Now if I just wanted convenience and didn't mind sacrificing a bit of sound quality then I'd still have the 64 GB cards.
I agree it's strange how firmwares impact sound and how much it can impact sound. But I've been accustomed to this since the Studio V then the DX100
. Wasn't really expecting the AK120 to change in sound though as I didn't notice the RWA unit do this. But I'm guessing on the newer firmwares it does indeed change the sound?