When I first started this thread the headphones were not appearing in lsusb. But then after the dmesg suggested by somedude they started appearing:

lsusb:

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 002: ID 0d8c:0001 C-Media Electronics, Inc. Audio Device
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

Yes I did alsa restart. In sound>preferences I've tried setting everything to alsa and also setting everything to C-media usb audio but unfortunately still no joy. I don't have pulse audio. The headphones were a cheap pair bought from Maplins, Yoga EM-178. They are 'call-centre' style with a mic as well. The headset is a standard pair with a jack, which you then plug through a usb dongle.

Thanks for your ongoing help with this.

The following things puzzle me:

1] When you modified alsa.conf to use your USB device instead of the 0 [NVidia ]: HDA-Intel - HDA NVidia0 [NVidia ]: HDA-Intel - HDA NVidia and restarted alsa, nothing should have come out of your speakers (which are connected to your on-board sound device), only your headphones. Maybe you need to double-check this all again?

2] There's little on the www about your device: Bus 002 Device 002: ID 0d8c:0001 C-Media Electronics, Inc. Audio Device, which either means it "just works" or there aren't many people using it.

3] Do your headphones work with anything else (eg any music player) ?

4] I hope you don't still have my script (even modified) running from rc.local, because if that is failing somehow it may be restoring your original setup for sound device 0 at the next boot.

So, trim things back to the bare minimum, and change one thing at a time. Test. Re-test.

HTH

Thanks to everyone who helped with this. I am now pleased to report that this problem is now solved! This link in an ubuntu forum helped:

http://ubuntuforums.org/showthread.php?t=1130384


Basically I wasn't using PulseAudio properly and was missing a few essential plugins.

Ah!

I did ask in post #15 if you were using PulseAudio. In post #16 you said "I don't have pulse".

But now it's Yes. Please make up your mind before you post in future.

Anyway - Problem solved. Well done.

Well I didn't have pulse audio when I wrote that, or at least it wasn't installed properly with all the plugins. Only yesterday had the pulseaudio shortcut appeared in the tool bar.

Your posts did help: over the weekend I managed to get the testing 'beep' through the headphones for the first time after re-typing the codes in terminal, then after a bit more tweaking I got them to work with media players. But I still had a problem with Flash sound. Then I saw the post I linked above, installed all the plugins he recommended, and managed to get pulseaudio to switch to the usb.