I installed NITdroid on my n900 just out of curiosity and I was amazed of the sound quality using internal speakers. The sound is A LOT softer without ANY distortion what so ever - even on full volume and the volume is about the same. There's also a lot more bass than maemo audio through same speakers.
With headphones it's not such a big of a difference, but still sound like there's less distortion.
So.. I figured out that there's sth wrong with how maemo5 handles the audio data or how it handles the hw responsible for amplifying the signal.
Is this component closed source? Maybe it'd be possible to port some of these from android to maemo?

IMHO PulseAudio was bad step in Fremantle development. Android use ALSA and it is much much better for mobile devices then PA.

Your explanation doesn't make sense IMHO. If I understand it correctly when reading http://en.wikipedia.org/wiki/Pulseaudio, PulseAudio itself is but an additonal layer on top of ALSA.
Perhaps Andorid uses ony ALSA without PulseAudio , but the latter gives many advantages in mixing and modifying the audio signals. Of course it can sometimes be a bit heavy for a mobile device - but then, the N900 is a computer And PulseAudio can also be found in the Palm Pre.
Anyway, PulseAudio is the way to go and an important part of the future of Linux.

Yes you are right. My explanation wasn´t whole. i am sorry. Yes PulseAudio is way to the future. Ubuntu is going to have it together with GNOME 3 and others, but IMHO for now it isn´t good piece of software for mobile devices.

Any clue why is this distortion happening in maemo, but not in android?

I have no problems with the audio.. Actually it's pretty good. i have not tried nitsroid yet so i can't compare.

I have the same issue
Headphones OK
Stereo Speakers - low bass, on max volume is not loud enough
In YouTube videos the volume is better.
I don't know about NITDroid. For me PR.1.2 is full with audio issues.

strange..
i coulda sworn pr1.1.1 had good audio quality
score one for nokia

I have never had any issues with audio - except the ringtone optimization thing.
(Maemo decompresses the ringtones into wav and saves them with a little lower quality, in order to make them play smoother.)

Other than that, music quality is great on my N900.

I have lowered my speaker volume.. cause it was to loud. Got it on ~70%. The headphone could need a boast though but is enough to be good.