Problem: The preferred connection for recording is via S/PDIF to stay in the digital domain. Many affordable sound cards don't provide zero/low latency hardware monitoring for S/PDIF inputs. The signal would have to be routed and monitored via DAW which inevitably adds annoying latency.
Solution: A simple solution without using external mixers is the headphone or main output of the Kemper for monitoring. These outputs provide the Kemper's signal without additional latency. Adding the playback signal to the headphone/main out can be done via Auxiliary input.
Added bonus: While recording the guitar dry (output source "Stack" or "Git / Stack") post amp effects could still be added to the monitor signal (e.g. modulation effects, delay, reverb, Headphone Space). This allows for comfortable guitar sound in the monitor while keeping all options for mixing mod and space effects later.
Note: The Auxiliary input will not work while using the Hardware Effects Loop in your rig.
The signal chain:
Kemper <-> Soundcard
S/PDIF Out -> S/PDIF in (for recording)
S/PDIF In <- S/PDIF out (for re-amping only)
Alternative Input <- monitor out R (playback )
Return Input <- monitor out L (playback)
DAW settings:
Route the monitor/playback signal to the audio out ports connected with Kemper.
Kemper settings:
Use Auxiliary input control in the output section to adjust the level of the monitor/playback signal.
Future improvements: Using 'S/PDIF In' on the Kemper for the playback signal is currently not supported. Maybe this could be added in a future firmware update. The advantage would be less cables and no analogue connections between Kemper and DAW.