The miller pipepro machine has option to set "arc control" which adjusts the length of the arc by I believe increasing the amperage. The lower the setting the shorter, more focused the arc is. Which is good when welding on edges. The higher the setting, the longer and hotter the arc is, giving a good wash out. And by the sound of the weld it seems that the pulse frequency increases with the arc length. Perhaps that's what changes the length of the arc? Hope this helps.
