Bogner 3534 ground loop hum

[BadCat]

That noise he gets when engaging the loop would be a dealbreaker to me (21:50-). Is this an inherent flaw to the 3534 or is his amp defect?
(2545) Marshall JCM 800 Vs Bogner Ecstasy 3534 - YouTube

 

[BadCat]

Sorry guys i should have written from 21:20.- on.