Does anybody have an idea what this hum might be?

[glip22]

It's probably from your power section. I believe you are at the sell the amp or live with it stage. I don't feel any tech will stop it as it can be considered normal for that amp. Not even Bogner stopped mine.

 

[Random Hero]

Hahah, no I won't sell. I'm just curious what it actually is!

 

[glip22]

Hahah, no I won't sell. I'm just curious what it actually is!

You'll never find out

 

[Prostage]

For any hum problems, check out this new Guitar Rig Building Guide:
http://www.prostage.eu/guitar-rig-building-guide.html
I'm almost sure that you can find the answer for your problem within this guide.

Lukas