Clean room is pretty low, by 10-11 o'clock it starts breaking up.
With humbuckers you get the edge of breakup around 11, singles around 12. From there it doesn't really get louder just more gainy. This is with the Master Volume at pretty much any setting. I think you have more headroom when the Master is turned all the way up, but I haven't cranked it that much so don't take my word for it.With a single coil guitar ou a humbucker one? You mean 11 o'clock on both the Gain and Volume knobs?