arc control usually is an adjustment that controls inductance, or resistance to voltage changes. there are more dynamics going on in that " flat line" dc cd curve than might be expected, especially when the arc initiates. it is almost always a try-it-and-see sort of adjustment and seldome make s difference to a troll like me, but real welder guys can feel it. it won't often show up on a static loadbank setup.
in years past linde printed a book which expalined it ALL. where you will get one of those very informative texts is beyond me, but they were hot knowledge in their day.
even in mainstream industry, arc control is sort of a mystery subject....soft arc.. digging arc.. whatever.. try figureing it out on a SAM 650. way plenty of knobs....

Spin,

If I understand your post you must have a Miller Synchrowave 250.

That particular machine has for reasons far beyond the understanding of mortal men, the need for the AC balence control to be set to 3 or (balenced) for best performance in DC- (DCEN). The folks at Miller told me this is a need specific ONLY to the Synchro 250 and the symptoms of leaving the thing in any other place but balenced is that you will have less feathering control in your foot pedal. We have had many 250s and have found Millers advice in this to be right on the money.

So yes, in most cases one need not think about AC balence control during DC operations. Its a bug specific to one machine, if you want to call it a bug.

We have a Sync 300, and it says the same thing...set to 3 for dc!