The invention provides for a printhead assembly for a pagewidth printer. The assembly includes a substrate channel, an ink hose, a support plate, an extrusion and a cover plate. The substrate channel operatively positions a plurality of printhead modules to form a pagewidth printhead module assembly. The ink hose is positioned within the substrate channel to supply the printhead modules with ink, and the support plate encloses the ink hose within the substrate channel. The extrusion houses bus bars operatively providing electrical power to the printhead modules, and the cover plate secures a flex printed circuit board (PCB) in the assembly, the PCB forming a data bus to the printhead modules.