A printing system comprising a pen comprising a number of print bars; each print bar comprising a number of printheads in which the printheads are grouped to a number of printheads from each of the number or print bars, the grouped printheads forming a slice and in which the printheads of the slice are electrically coupled to a common power supply unit. A printing pen comprising a number of print bars in which each of the number of print bars comprises a number of printheads, in which the number of printheads are grouped together to form a slice, the slice comprising a printhead from each of the print bars, and in which the slice is powered by a common power supply unit.