Hi,
I've read something similar from several years ago and I think it needs a solution.
The manual says that you can use return 1/2 on the Kemper Stage to feed an auxiliary signal into Main, Monitor and/or Headphones outputs using an "mp3 player".
Headphones volume around -33 dB gives me enough volumen to play with IEMs connected to the headphones output, but when connecting my iPhone/iPad to the aux in you just hear a tiny little signal, and obviously you can't play over it. At 0 dB it sounds like a regular volume, not even a little high.
I don't know if by "mp3 player" they're referring to a mixing desk that can drive the internal Kemper aux input amplifier, but obviously the devices that everyone could use to feed an "auxiliary input" will be smartphones or tablets mostly.
Is there any solution? I've even tried to bounce the mono file with the fader of the track and the output at +6dB and it just distorts the signal, and I don't think that the solution is messing around with every rig volume to adjust it just for playing occasionally with an auxiliary input.