Please note that no portable audio player with any lossy(or even lossless) codec will give you "natural sound"...as far as that term can be defined...
While I do agree with the fact that the higher your source is the better it will sound its also true that your sound depends much on your earphones, settings and personal preferences
I myself use a Shure set with my Miniplayer and the quality of music is fine.
Way better than the Ipod Video I had and better than the Archos I had.
However, it doesn’t sound nearly as clear and full as my 8 year old Yamaha stereo with good speakers
why? because I use mp3, on a small player, with earphones that simply dont have the room to resonate like normal speakers, usually in a less than silent environment(isn’t that what we all use Mp3 players for?)
Sound quality is largely a matter of personal preferences.
Therefore, debating about the "best" EQ setting is useless..
I use the classical EQ with slightly increased bass.
With bass boost and treble boost on 0 Spatializer on “on” normal, Virtual 3D off ,PCE on 3, VIBE on 0, Speaker type earphone
Is that the best? It is for me... probably not for the next guy with different music choices, codec preferences, ears and earphones…
Just my 2 cents…
