I have no sound issues - I believe that the sound is setup by these lines in ukchan30.c
Code:
#ifdef NICAMSTEREOMODE

        /* setup NZ (NICAM) ONLY sound - see page 22 of msp34x0g_4pd.pdf */
        iicw4(0x88, 0x10, 0x00200008); /* B/G NICAM Stereo (only) */
        /* not sure if you need to do this step as manual is a bit vague but we'
ll leave it in the code as it may be useful */

#endif
I definitely get clear sound, and can hear that it is in stereo.

This module does nothing to set up the output channel - though I could make it do so with a bit of investigation into iicset parameters I suppose. In 2.5.5 the mainline code would do the setup as it's designed to do so, and for real US models the code in palmod has this code. I'd try doing it from shell script but for come reason the iicset from the OzTiVo distribution just segfaults when I run it...

Of course I will get a bigger hard drive soon, and the magic of the Thomson image will make all my problems go away :-) But I have had fun learning all sorts of stuff about the TiVo that I never really thought I would need to know!