Hi christophe, i use the line input 1 but i did the test with the 2 and there is no change.
Sorry but i don't now what is High Z input.
I don't want to use front input cause they are preamped.
Even i could find an astuce i don't want to make profile with not a good (same) guitar level (my first try with the first one make saturate the amp so the profile)
The inputs on your soundcard may all be with lower impedance (low z) and not suited to take the guitar direct. It puts too much load on the guitar, that might change the sound and volume. Please check if an high impedance or instrument input is mentioned in the manual of your audio interface.
The input of the Profiler is high impedance and perfectly matches the guitar. The Direct Out on the other hand is low impedance and will match easily on all inputs of your soundcard, preserving the correct volume.
In other words: the direct out helps to interface your guitar to your audio interface. The higher volume is a good indicator for a good match.
The only thing to solve the situation is simpy lowering the input gain of your sound card to avoid clipping.