An apparatus renders a plurality of graphical objects of an image on a scanline basis, with each scanline including at least one run of pixels, and each run of pixels being associated with at least one of the graphical objects such that the pixels of the run are within the edges of the at least one graphical object. A storage circuit includes memory locations having contents accessible as a function of the digital value. The tip electrode may have a set of grooves or cut out regions in its outer surface to provide edge effects for currents applied through the tip electrode. In the L channel and the R channel, DC addition voltages generated by DC dither circuits are different from each other. Fifth and sixths amplifiers have an input that communicates with the output of the second and fifth amplifiers, respectively.