Like most systems you cant' use both outputs at the same time. Changes
are mode vis System/Administration/Sound.

You can buy a switch that allows you to one button switch between the
two sources.

I must not have explained well enough. I am not trying to use headphones and
internal speakers at the same time. I am trying to input audio from an
external
receiver to the the line input of the internal sound card, then listen
to the amplified
audio. I can see the audio on the input but get no audio out the
speakers., this on
both systems both running Ubuntu 10.04. The note about plugging in the
headphone
is to say that for some reason Ubuntu does not recognise the activation
of the plug
either input on the line in or line out.
Now I would like to report the problem to the Ubuntu developers and
can't find out
how, and I am a member the forum but it isn't obvious as to how to do that.

Try going through all the hardware options in Sound Preferences as
your sound card might work better with something other than the
default setting that's applied on install. Also it might sound silly
but if you have a surround sound card ( i.e. more than 3 sockets ) the
sockets are not always mapped as marked so it's worth plugging into
different ones and seeing what you get whilst trying the hardware
options.

You should be able to feed in through line-in or microphone and hear
the output through the speakers - just a case of getting the settings
correct for your hardware.

BTW - the main reason for this problem is sound chip firmware that is
written to use Windows API's for processing rather than doing it on
the chip. It's a cheaper way of developing the firmware but can cause
hiccups for other OS's !

Well only has three input jacks on this old PC, Line-in, Line-out and Mic.
Got on line and verified the symbols on the back are as I interpreted
them. The software preferences have all kinds of settings, so I went to
my music folder and clicked on some music and played with the options
until I got music out of the speakers.
I have downloaded Debian and got it loaded on that PC, and loaded the
software that is controlling the receiver and have the line in as before and
I get sound out of the speaker without any fiddling with the settings.
So I think there is a problem with the Ubuntu 10.04, 10.10 sound settings.
I am still going to play with the laptop and plug it in running 10.04 to
see
if I can find out what is missing. I do have a clue, it may need ALSA Mixer
downloaded and installed. The Debian load has it as the sound control
and I don't see it in the Ubuntu load.

if you think it is one, should be reported to Launchpad, but search
first to see if someone has reported the same thing.
https://launchpad.net/ubuntu

Thanks for the link, and can I check there for this problem to see if it
has been
reported and if there is a solution?