Nice that you solved that part for yourself 
As for the main issue of this thread.
If your alsamixer first page still looks like this: http://www.subirimagenes.com/descargar.p...409&tipo=6 (btw. very bad image uploading site. Crashing my browser here and spams even with adblocking in place like crazy. Perhaps for future reference use imgur)
then it clearly shows that line and rear mic channels are muted (the MM means Muted both channels).
To unmute navigate with the arrow keys to the channel like line and hit m key which toggles between mute/unmute. Both channels should have green 00. After that I guess the volume is too high you can change the volume with arrow down aswell.
That should make it possible to hear everything coming from either Line or the Rear Mic.
As for the main issue of this thread.
If your alsamixer first page still looks like this: http://www.subirimagenes.com/descargar.p...409&tipo=6 (btw. very bad image uploading site. Crashing my browser here and spams even with adblocking in place like crazy. Perhaps for future reference use imgur)
then it clearly shows that line and rear mic channels are muted (the MM means Muted both channels).
To unmute navigate with the arrow keys to the channel like line and hit m key which toggles between mute/unmute. Both channels should have green 00. After that I guess the volume is too high you can change the volume with arrow down aswell.
That should make it possible to hear everything coming from either Line or the Rear Mic.
