using ubuntu 14.04.1 on a amd chipset with realtek audio
scb@scb-desktop:~$ uname -a
Linux scb-desktop 3.13.0-33-generic #58-Ubuntu SMP Tue Jul 29 16:45:05 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

scb@scb-desktop:~$ lspci | grep Audio
00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA)
01:05.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] RS780 HDMI Audio [Radeon (HD) 3000 Series]

some time ago I lost my 5.1 output setup and hoped it would come back with the Trusty upgrade. it didn't. I used to see an option allowing me to choose 5.1,6.1,stereo etx and now the option is gone. alsamixer shows front center, but no real left, rear right and bass.
please, advise how to fix.