When everything is wired and working right, the Two Stroke is a pretty quiet little amp so it sounds like what you have is not “normal”. Of course, there will be *some* noise but if its going away when the tone is maxed, then there is likely some issue.
Can you describe a bit more about what is happening? Is the hum always the same volume or does it increase with the volume increasing? When the tone is maxed and it goes away, does everything else sound normal? Has it always been there or did it just start? Stuff like that.