Hall of Fame 2 Mini audible click in sound

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I have an audible click in the sound when I switch on or off the Hall of Fame 2 mini pedal.


I tried with different power sources (Boss, 1-Spot, Powerbank) and it is still there, even when the pedal is the only one in 


the chain. What can be the problem (software or hardware) ?


Thank you


Greetings from Belgium