There is definitely a problem with the Kemper headphone jack when using high gain profiles for metal. The profiles sound good through FRFR speakers or when recorded, so they are fine. 3 other Kemper users around the area and I used different headphones like ATH-M50x, Beyerdynamic, Sennheiser and they all have the same issue. The headphones are great when listening to music from other sources, or when using Kemper headphone jack with clean, bluesy or rock sounds. But with high gain profiles, they sound very harsh and quacky. Changing Space parameter, PureCab or initializing settings do not help. You can EQ and filter out treble or change cab high shift setting to mitigate a little bit, but why would somebody want to do that just for headphone jack and change characteristics of a profile. You can test this with the Lesse Lammert metal profiles that come with factory rigs. Not sure if this is a hardware or a software issue, but it needs to be fixed by respected Kemper engineers. Please help!