AC97_EXTENDED_C_LFE_VOLUME_REGISTER
ac_mono_set(ctrl, value, AC97_EXTENDED_C_LFE_VOLUME_REGISTER, 0);
ac_mono_set(ctrl, value, AC97_EXTENDED_C_LFE_VOLUME_REGISTER, 8);
ac_wr(ac, AC97_EXTENDED_C_LFE_VOLUME_REGISTER, 0);