SPDIF on VIA EPIA board

[Dag-Erling Smørgrav]

I have a VIA EPIA MII board with an RCA connector which can be
configured as either composite TV or SPDIF via a jumper.  The jumper
is set correctly for SPDIF, but my amp (NAD T751 A/V receiver) does
not detect any signal coming from the computer.  The amp works fine
with other SPDIF sources.  The EPIA board works fine with speakers or
headphones connected to the minijack line-out connector.

pcm0 at pci0:17:5: class=0x040100 card=0xaa011106 chip=0x30591106 rev=0x50 hdr=0x00
    vendor   = 'VIA Technologies Inc'
    device   = 'VT8233/33A/8235/8237 AC97 Enhanced Audio Controller'
    class    = multimedia
    subclass = audio

# cat /dev/sndstat
FreeBSD Audio Driver (newpcm)
Installed devices:
pcm0: <VIA VT8235> at io 0xc400 irq 5 kld snd_via8233 (5p/1r/1v channels duplex default)
# sysctl hw.snd.pcm0 dev.pcm.0
hw.snd.pcm0._buffersize: 4096
hw.snd.pcm0._vchans: 1
hw.snd.pcm0._vchanrate: 48000
hw.snd.pcm0._spdif_enabled: 1
hw.snd.pcm0._via_dxs_src: 0
dev.pcm.0.%desc: VIA VT8235
dev.pcm.0.%driver: pcm
dev.pcm.0.%location: slot=17 function=5 handle=\_SB_.PCI0.AC97
dev.pcm.0.%pnpinfo: vendor=0x1106 device=0x3059 subvendor=0x1106 subdevice=0xaa01 class=0x040100
dev.pcm.0.%parent: pci0
dev.pcm.0.wake: 0
# mixer
Mixer vol      is currently set to  75:75
Mixer pcm      is currently set to  75:75
Mixer speaker  is currently set to  75:75
Mixer line     is currently set to  75:75
Mixer mic      is currently set to   0:0
Mixer cd       is currently set to  75:75
Mixer rec      is currently set to   0:0
Mixer igain    is currently set to  75:75
Mixer ogain    is currently set to  75:75
Mixer line1    is currently set to  75:75
Mixer phin     is currently set to   0:0
Mixer phout    is currently set to  75:75
Mixer video    is currently set to  75:75
Recording source: mic

DES
-- 
Dag-Erling Smørgrav - des at des.no