No the muting isnt the problem. I dont think the earphone socket is even on when Linux is running since the red light is not on.
The sound card comes up as:
Intel Corporation 82801/FBM/FR/FW/FRW (ICH6 Family) High Definition Audio Controller (rev 04)
Subsystem: ASUSTek Computer Inc: Unknown device 1113
Flags: bus master, fast devsel, latency 0, IRQ 201
Memory at feb38000 (64bit, non-prefetchable) [size=16k)
Capabilities: [50] Power Management version 2
Capabilities: [60] Message Signalled Interrupts: 64bit+ Queue=0/0 Enable
Capabilities: [70] 10 [0091]
Thanks for your help so far