Amarok was working for me until a few days ago -- and then it lost its voice entirely and stopped producing sound. Yet other applications are still producing sound, and even the Phonon test within Amarok itself produces sound. I do have one unsolved, relevant problem: pulseaudio gives the message "Daemon startup without any loaded modules, refusing to work." However, that isn't enough to stop the Phonon test from working.

Update: The sound just came back as mysteriously as it disappeared -- after plugging in my Sansa Clip+ mp3 player. I got a couple of messages about nonworking sound drivers but they disappeared before I could transcribe them. Go figure.

I recently upgraded to Kubuntu 11.04 with Kpackagekit.
I believe that something was messed up in the sound system, but I'm confused.
I had been using (and want to continue) Logitech USB headphones for sound, including enjoying it from Amarok: 2.4.0 on KDE 4.6.3 (Kubuntu)
The headphones work for system sounds, browser sound, banshee (which I installed after encountering the problem).

If I start Amarok, I get a notification:
Switching to the audio playback device Internal Audio Analog Stereo
which has higher preference or is specifically configured for this stream.

Even if I choose "Revert to USB headphones" the sound goes through my laptop speakers. Laptop: Acer Aspire 5820T.

System restarts have no impact on the problem.

System settings have the USB headset as the preferred device for all Phonon settings.

The obvious problem is that Amarok is handling sound differently from those other programs, since it was the same, the result would be the same.

I'd check the Phonon settings, which you can get to in two ways at least:

1. In Amarok, go to Configure Amarok, then Playback, then Phonon.

2. In the main Systems Settings, you can get to Phonon via Multimedia.

As far as I know, accessing Phonon in either ot these ways produces the same behavior. If some apps go through Phonon and some don't, that might provide a clue.

One question that needs answering is whether the difference arose because something happened after various applications, etc., were started or instead was already there when you first logged in. So rebooting, or simply logging out and logging back in again, may show you which of these is the case.

Two other experiments that might yield useful data:

1. Plug and unplug the headphones -- twice.

2. Start up Audacity and see what happens to its output, after you've configured it as best you can.

I hope you're not dealing with a so-called Heisenbug (after the Heisenberg Uncertainty Principle in physics), where every attempt to diagnose the proble provokes the problem.

Forgive me if I'm only restating stuff you've already thought of ten times.

The Linux sound system is acknowledged to be a godawful mess, with overlap of functions at different levels. Just try to figure out the interaction between pavucontrol and alsamixer!

Good luck!

Audacity plays through the headphones.
Thanks for the test suggestions, pwabrahams.
I've tried all...to no effect.
I'm still thinking the upgrade is involved, somehow. The problem isn't critical, and may be cured by the regular progression of bug squashing that happens in the weeks/months after a new major distribution release.

My main purpose was to report the issue. I've also put the info onto a mailing list of Ubuntu.

Is your system using Pulseaudio? If it is - which it would be if Audacity is obeying the settings in System Settings - then ensure your current Phonon backend has the Pulseaudio modules it needs installed. (Pulseaudio support in VLC is a seperate package for instance)

One other thought. Look at the third tab of pavucontrol (Output Devices). Does it show your USB headphones at all? Are the headphones a possible choice under "Port"?

My system (Kubuntu 11.04) did not have pavucontrol installed.
After installing it and its dependency library (didn't record which), I looked at the third tab as suggested.
The USB headphones were listed and not muted for output.

I decided to launch Amarok to see if the pavucontrol installation had made a difference. No sound from my headphones. Then I looked further around the tabs of pavucontrol. On the main tab, "playback" Amarok was listed third after two knotify instances. The two knotify volume bars matched my normal taskbar volume control. BUT Amarok was shown as muted.

When I clicked the muting button, the headphones came right up.
So, here's the follow-up question. Did the upgrade to Natty set the USB-Amarok connection "off" somehow? I'm guessing yes.

None of the other controls showed the Playback of Amarok as muted, but pavucontrol did...and provided a simple fix.

Next, I'm going to do some more testing, including restart, etc. I'll report back. Right now I'm listening happily to Acoustic Alchemy's "Take Five."

Thanks.

[[Restart Update]] With no other steps needed, I was able to start Amarok and have it play through my USB headphones.

I believe that the popup notices I was getting before, telling me that the sound was switching to the internal speakers was caused by the mute setting for Amarok. Within Amarok, I could not locate any setting/control for muting. My system volume control didn't control the problem. Apparently the pavucontrol tool was able to access the setting which had muted Amarok playback. A simple click in that tool, and all is again well. I'll pass the information along to the Kubuntu people so they can check to see what "fix" needs to be done for Natty. I am sure I'm some sort of edge case, but maybe not. The only reason I use the USB headphones is that the speaker port/socket on my laptop (Acer Aspire 5820T) didn't provide sound for regular headphones. It is a combination port including s/pdif, but didn't perform for me as a simple audio socket.

If you have a Pulseaudio enabled KMix, it can be done from there as well, from the "Playback streams" tab.

When I open the mixer window from my system tray volume control it shows just wide enough to see the first two tabs...typically, I didn't look further than that!

Thanks.

I was glad to learn about the pavucontrol program, though. A variety of tools is one of the good things about FOSS. Many eyes and the kindness of others found on forum discussions is the other big benefit.