I've done it to my Fuze. I got it from Tiger Direct Quality RefurbishedLucky me it was a v.01. So I bought in hopes of rockboxing. And YES! I WIN.
So those details out of the way...
On to the rockbox...
You get well hammered on Firmware. ROCKbox. Which comes with the "featureset" including: Custom Channel Configuration, Stereo Widening, Crossfeed!!!, Graphical EQ (with frequency filtration, wideness, and levels of course), as well as dithering, and then ReplayGain with a preamp level, and clipping prevention.
HERE is my ROCKbox setup. I like it loud, I like it wide, I like it dynamic n 3D. its killz. Play around, adjust to your taste. Its an endpoint for me, maybe a pistolshot to begin the race for you? Have Fun / Ask Questions.
a ROCKbox EQ adapted from the Head-Fi.org user HiFlight's settings as reposted on Xin's Cool Talk forum.
Modified after much twiddlesomesuchnessessnes by YOURS TRULY with much experiental toying with a range of COWON, iRiver, and other DAPs... and now the s:flo2, and re-fixed on the sansa Fuze.
Direct Gain: -3.5dB
Cross Gain: -6.5dB
High Frequency Attenuation: -16.5dB
High Frequency Cutoff: 700Hz
LS: 9.0 dB / 20Hz / 6.0 Q
PK1: -3.0dB /600Hz / 4.0 Q
PK2: 7.0dB / 4000Hz / 3.0 Q
PK3: -2.0dB / 8500Hz / 2.0 Q
HS: 4.0dB / 16000Hz / 5.0 Q
ENJOY. this is an AWESOME SOUNDING setup. I enjoy it muchly on the ROCKboxed sansa Fuze v.01 hardware.
as extracted from my post on iAUDIOphile.net's forums....
It is a very configurable firmware. You can always dump your settings to
Settings > Manage Settings > Save .cfg file
Settings > Manage Settings > Save Sound Settings
Settings > Manage Settings > Save Theme Settings
and then you will have completely backed up settings files from which to restore your rockbox state before monkeying around with anything.
you can just copy your .rockbox folder on the device while on windows, macos, or linux and save it to another safe location as a full on backup. as a complete archival backup.
BTW, rockbox is 3-5 TIMES better than the Sansa Firmware to ME. it just has better audio renderering TO BEGIN WITH, and then you add the feature set and the crossfeed, the replaygain, the graphical EQ, the stereo widening.. its CAKE! that you get to eat too!