Most interfaces these days list a specification of what the maximum input level is in dBu. It can be a useful value to know, especially when recording DI's and reamping when using a variety of different DI boxes and reamp boxes, as well as different converters (which can have their own dBu to dBFS reference).
I just measured the Kemper's Input headroom and also the Direct Send (used for profiling, but also reamping). With all input and output settings (clean sens, reamp sens etc) at unity/0 , I measured pretty much exactly 5dBu for the DI and reamp headroom.
The video's above show how you can work this out using sine wave's, a multimeter, and some maths equations.
I also tested recording DI'd guitars with these settings at 0 - they seem very loud and are audibly clipping.
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If I reduce the clean sens. to around -7dB, then my input headroom is 12dBu. In this setting, there was no audible clipping and the levels look healthier. This is more typical for many "prosumer" type devices. UAD Apollo's and Focusrite 2i2's have their maximum input level for their DI's at 12dBu - more high end converters typically allow you to adjust, but they can go up to 24dBu or so (so nearly 20dB more headroom than Kemper at default settings!).
The manual states:
Which suggests that having a very high DI signal is expected if you don't adjust "Clean Sens".
Is anyone able to verify 5dBu is correct?
If anyone is using a Kemper as a DI recording device for using with other amp sims, or for reamping later, I would suggest the -7dB/+7dB settings above as a minimum.