Ok, found out, that issue is not present, when connected to another sound card. But on sound card, where problem is present, the problem is only with Kemper, not with other devices. Can common grounding problems be only around 50Hz? Or high frequency noise also possible?
Maybe Kemperr Power Supply
Powerhead? Class D amps hiss, it's very common. Even IcePeak.
No, not powerhead. Plugged directly to soundcard from main outputs.
Power to Kemper goes through Furman power conditioner. But tried also through simple plug.
Did anyone experienced this noise when connecting through main output XLR cables?
Is is almost not hearable, but I assume it shouldn't be there.
Tried different cables, ground lifts - nothing helped. Is present even when output volume is set to -infinity and every module is switched off.
Not present when running through SPDIF.
Also disappears, when Kemper is switched off, so shouldn't be cables.