Extremely loud hum when profiling. (UPDATE: hum gone, loud hiss instead)

    Hi folks.

    I've had the Kemper for quite a while now and made a ton of Kemper profiles at a studio with a friend's Kemper before with no issues, but I finally moved on to set up my home studio to do profiles by myself. I even recently got the KPA DI box so I could make direct profiles.

    So I set everything up by the books, turn on the amp and there is an extremely loud hum. I went through the manual time and time again and read the part about a possible ground loop and what not, but I can't seem to fix the hum issue at all. I played with all the ground/lift buttons on the back and tried several combinations. And it doesn't matter whether I try to make a studio profile with an SM57 in front of the amp or a DI profile with the KPA DI box.

    I also checked the cables and tried all of them with a guitar straight into the input of the amp and everything sounds normal, so the hum is def being sent from the Kemper direct out/send. Pushing the ground lift on the direct out/send makes it worse - so if anything, it goes from very loud hum to very very loud hum. This is the lesser loud hum:

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    Does anyone have an idea what could be causing this? I am running my studio rig as follows: wall plug -> surge protector -> Furman M-8Dx power conditioner -> Kemper. The reference amp is also on a surge protector over in the next room.

    I'm out of ideas. Hopefully some of you can help!

    Thanks.
    Simon

    So, this actually worked! The hum is gone, only your usual hi gain hiss is still there, as to be expected.

    BUT... I have a tubescreamer type pedal in front of the amp that I wanted to be part of the profile, but now that one is extremely loud - only in conjunction with the Kemper, though. It intensifies the hiss to unhealthy levels.

    The pedal is an integral part of my sound, so I'd rather not do without it. I tried a different tubescreamer, just to see if the issue is still there, but same thing.

    Update:

    So while the hum is gone, it seems like the "hi gain hiss" is still louder than it should be once the Kemper is hooked up to the amp's input, and essentially becomes unbearable once a tube screamer comes into play.

    I'm running both, the Kemper and the amp, powered by my Furman power conditioner. I switched my tube screamer to battery powered to see if that would help, but the problem remains the same. The hiss just gets insanely loud.

    Here's a video where you can see and hear the three stages of hiss:

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    1st guitar straight into the amp's input
    2nd Kemper straight into the amp's input
    3rd Kemper through battery powered tube screamer into the amp's input

    Any ideas?