The PowerPlant Metal Halide SuperVeg (also known as retro-fit) lamps run off High Pressure Sodium control gear, and are ideal for vigorous vegetative growth.
There is no need to have two different ballasts, simply use the SuperVeg lamp during vegetative growth, and change to the PowerPlant Super HPS lamp for flowering, all using the same HPS ballast.
This allows the grower to give the plants the perfect Grow spectrums and Bloom spectrums for optimum plant growth, more compact plant structure and amazing high yields, while only needing one ballast.