Originally Posted by HDH
I'm using a Creative Zen Vision:M with WMA files through my E90 and the volume is fine for most ripped CDs. Some of the older ones dating back to the late 80s early 90s seem to be significantly quieter but all the latest stuff will go more than loud enough to make my ears sore. A mate of mine has found that ripping his CDs to his iPod produces lower volume recordings than downloading from iTunes so I guess there's some mileage in the volume possibly being configurable - don't know how though as it doesn't seem obvious with the Creative software.
All digital music has varying base volume levels (gain).
There is a little free utility called mp3gain which can solve this.
Essentially the best bet is to normalise everything at 89 dBA using this programme. This not only levels out the volume it stops clipping (which would otherwise muddy or distort the sound).
Normalising the volume doesn't get rid of volume changes with the song - just from one song to the next. You can also normalise an album - so a quiet song stays relatively quiet compared to the rest on the record.