Played it for the first time tonight,,,sounded great, lots of growl,,I played a American P Bass with TI Flats... but I did notice some buzz, ..I was set at about 11:00 vol,,,
Were you hearing buzz from the cabinet? That could be a number of things. Best thing might be to take a cardboard or PVC tube (whatever's handy) and try to find out where it's coming from.
Possible causes if it's from the cab might be
1) bad driver
2) loose screws or glue joint
3) puffing out the back of the cab from the 1/4" jacks, though this sounds more like a whistle