I have just checked 2 different Butterslax profile, number 3* was clean and Butterslax4m was muffled as hell.
I also tried with headphones(only connection with KPA) and it was worse. The sound was clipping and buzzing so hard. All these process have been performed after contacting Kemper Support Team. Here is the message from Kemper Support. They are pretty helpful and willing to help by the way.
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thank you for your email.
Maybe the previous owner applied some odd settings that are causing your issue.
Please try the following approach to reset the unit to its factory default state:
In order to reset the PROFILER to the factory default state please perform the following steps:
1. First, consider creating a backup as this process will delete all user data and reset all global settings.
2. Upgrade to the current PROFILER operating system release software. The steps are described in the manual.
3. Switch the PROFILER Head or Rack model off and press and hold soft button 1 (left above the display) while powering it on into tuner mode. If you are a STAGE user press the soft button 1 and the SYSTEM button and power the unit on.
4. Keep holding the soft button until "System Maintenance " appears on the display.
5. In maintenance mode press "Recovery", "Flash Init", "Yes", "Ok".
6. Then press the EXIT button and reboot or simply restart the PROFILER with the chicken-head knob. The PROFILER will now start with a single rig named "Crunch".
7. Restore the attached backup from a USB memory stick. The process is explained in the manual. The PROFILER will restart automatically.
8. Switch the PROFILER off.
9. Press and hold the two buttons RIG and SYSTEM while powering the PROFILER on. Keep holding them until you see "Initialising global settings" and "Initialising current rig" in the display.
The PROFILER will now start as a brand-new device and you will be asked to confirm date and time and enter an owner name.
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I followed all the steps before trying any of your kind suggestions but result is the same. I feel like there is malfunction with my KPA.