I've got my HTPC running Ubuntu 9.10, Pulse audio removed as recommended by the XBMC guys. The sound "card" is integrated Intel ICH6 on a Dell Dimension 8400. It's doing 6 channel analog out to my Logitech system via 3 1/8" miniplugs.

Everything sounds fine with music, and movies with a stereo soundtrack. I can even flip an option in alsamixer and it will spread the sound to all speakers, which is great for music.

But when I play something with an AC3 soundtrack, the center channel sounds horrible. Really tinny, like it's turned up too loud. I've tried lowering every option in alsamixer so nothing is maxed out. I've replaced the Logitech center channel with another "real" center channel, sounds the same. I've tried switching Center/LFE to use another jack on the back of the PC. I've tried switching the center channel to another input on the amp. Everything hardware seems to be fine. Also if I connect my iPod to the Center/LFE jack, it sounds fine.

I do have a center channel volume adjustment in ALSA, but it doesn't do anything. The center channel volume is controlled by the same slider as the surround speakers.

Also, the problem isn't just with AC3 in XBMC, it also does it when I run speaker-test. I'll post a sound clip if I can get a good one.

Any ideas? I suppose I could buy a new sound card, but that's kinda a last resort.

boot into windows and test it

I'd have to install Windows first

I have it running Linux because, among other reasons, the Linux version of XBMC offloads the decoding of most videos to the video card (a 9600gt with HDMI)

It's nice being able to play a 1080p MKV and have it sitting at 8% CPU usage. (3.4GHz P4 HT)

You could get a live cd of a different distro and see if that changes anything.

Well, most don't come configured to do 5.1. It was a fight to get it to work at all. It seems like it wasn't doing this at first though. That's why I got the new center channel, I just assumed this one had blown. Only paid $25 on craigslist anyway.

I guess I could try an older version of Ubuntu, but then I can't update XBMC via apt-get.

heh, linux sound

Came here to say this.

Maybe try OSS4?