I have bought a secondhand Little Big Muff, but it has a terrible buzzing noise when you turn it on, even when the guitar's volume is off.

Anyone had this problem before? It's the only pedal I use, and I think my cables are ok.
It's a big muff, it's going to be noisy as hell no matter what
-Giablo JTM45
-Hook 2X12
-fender hw1 strat
-Fender AVRI 62 strat