Problems with sound on a G5

I have a PowerMac7,2 that I cannot get sound working on. If I unmute the sound using Sound Preferences usually it immediately mutes itself again. Maybe one time out of three it will stay unmuted until I play a sound then it will mute itself again. When I play a sound I do hear it, but it is at a very low level even though I have Master and PCM cranked way up with alsamixer. I have also blacklisted the snd_powermac module.

scott@G5S-UM16:/var/log$ lsmod | grep snd
snd_aoa_fabric_layout 16922 1
snd_aoa_i2sbus 29492 1
snd_aoa_soundbus 8172 2 snd_aoa_i2sbus,snd_aoa_fabric_layout
snd_pcm 156552 1 snd_aoa_i2sbus
snd_seq_midi 11204 0
snd_seq_midi_event 11581 1 snd_seq_midi
snd_rawmidi 40537 1 snd_seq_midi
snd_seq 99703 2 snd_seq_midi_event,snd_seq_midi
snd_aoa_codec_tas 17289 2
snd_seq_device 9176 3 snd_seq,snd_rawmidi,snd_seq_midi
snd_timer 38709 2 snd_seq,snd_pcm
snd_aoa 25754 2 snd_aoa_codec_tas,snd_aoa_fabric_layout
snd 123886 11 snd_aoa_i2sbus,snd_aoa_codec_tas,snd_seq,snd_aoa_fabric_layout,snd_timer,snd_rawmidi,snd_seq_device,snd_pcm,snd_aoa
soundcore 11767 1 snd

One interesting thing is that sound works in Debian Wheezy on the same machine with the following modules.

scott@G5S-UM16:~/Documents$ cat wheezy.lsmod | grep snd
snd_aoa_codec_tas 16475 2
snd_aoa_fabric_layout 15593 1
snd_aoa 19158 2 snd_aoa_fabric_layout,snd_aoa_codec_tas
snd_aoa_i2sbus 25707 1
snd_aoa_soundbus 8274 2 snd_aoa_i2sbus,snd_aoa_fabric_layout
snd_pcm 97042 1 snd_aoa_i2sbus
snd_seq 66910 0
snd_seq_device 10190 1 snd_seq
snd_timer 28225 2 snd_seq,snd_pcm
snd 80572 10 snd_timer,snd_seq_device,snd_seq,snd_pcm,snd_aoa_i2sbus,snd_aoa,snd_aoa_fabric_layout,snd_aoa_codec_tas
soundcore 10667 1 snd
snd_page_alloc 10873 1 snd_pcm

Thanks in advance for any ideas.