In Analogue mode (default for non-10k2 cards):
PCM Volume is const (=0 – no attenuation); Master Volume is const (=0); Surround Volume is const (=0); it is possible to record / monitor one analoguesource only via 'Rec Source'; all ac97 input volumes are set to 'mute'; if unmuted they go directly to Front Speakers. Using 'StereoMix' mode or unmuting ac97 outputs is not recommended. Volume is controlled via DSP ac97in (in0/in1).
In “Digital Output Only” mode
AC97 PCM, Surround and Master Volumes are muted; “Rec Source' is 'StereoMix'; this allows multiple analogue sources to be recorded / monitored (with or without PCM – depending on kX DSP settings); input volumes can be controlled separately. One should unmute desired AC97 analogue inputs. Volume is controlled by ac97 source volume and DSP's ac97in (in0/in1).
The 10k2 is capable of recording multiple analogue sources when its PCM volume is set to 'muted' and front output goes to I2S codec directly; AC97 output is muted by default; input volumes can be controlled separately; DigitalOutputOnly does not influence AC97 codec; there is no AC97 'surround' output – I2S is used instead.
The Audigy2-based boards use AC97 codec for recording only. That's why the default signal routing is different compared to 10k1 and 10k2 (Audigy) boards. The AC97 codec outputs are always muted, thus, not affecting front/rear/center+lfe outputs. The 'i2s codec' shown on the diagram above (marked '10k2 only') is used for all the analog outputs.
Audigy2-based boards also have a special 24/96 unit called 'P16V'. More details can be found in here.