Buzz from amp before I plug in my tele???

Hey guys,

Whenever I turn on my Randall RG75 i get an awful buzzing from the amp. Tried it with all my guitars and the hum is the same. Only increases minimally when the guitar is plugged in. No valves so I shouldn't have to worry about that. I've tried it in different sockets around the house and without my pedal board. Hum disappears when either volume or treble is turned to zero. Any ideas what it could be?

Thanks in advance.

Your input jack may not be grounding properly.

Could be anything from cheapie cable,to bad ground connection.