A decorative cover for the handle of a dental instrument of the type having a shank and a tip for carrying a drilling or grinding tool. An outphasing amplifier includes a first amplifier and a second amplifier. The two chromaticity groups are substantially equally away from a target chromaticity in directions reverse to each other. Each of the first set and the second set is spread out laterally in a direction from an entrance end of the guide ramp to an exit end of the guide ramp to accept respective stacks of inter-nested articles from an upper row and a lower row of a trim press and transfer the stacks into a common exit row. The loop priming logic module is arranged to set a power reference value for controlling the power amplifier prior to a ramping operation of the power amplifier and the switchable logic module switching the switchable outer digital loop on or off, thereby restricting adverse transient behaviour of the power amplifier. An orifice can, for example, extend from the main coolant inlet to the second deflection region.