Are you saying that you can use a 400 watt bulb in a 1000 watt galaxy ballast? I may be confused as to what you want to accomplish,but I use a 1000 wat MH with the ballast in veg and use the dimmer in that phase of the plants life and full power at flowering. All this is with a 1000 watt bulb.You can't turn the ballast to low setting and put in a 400 or 600 watt lamp. Am I on the right track as to what your looking to do?