@ neutron bob
Thanks for looking into my type of problem! So “firmware descriptor” is the key word to look for!
As far as my audio files are concerned, I already came across Version 1.3.4 Beta of MP3Gain on some download site of a computer magazine, but there under supported operating systems it listed only Win 98, Win NT 4.0, Win 2000 and Win Me. So I am trying Audacity 1.3.11-beta right now and specifically the amplifying option available in the effects menu where Audacity automatically calculates the maximum amount you could amplify the selected audio file without causing clipping. It lets you even mark the option to amplify above dB 0,0, but I wonder whether this would be good for the Fuze and especially my ears. I think if I just could cut away or reduce those few peaks then the main part of my audio files could be amplified without clipping. Since I am not a great expert in working with audio files, it might take me some time though.
