Abstract: The disclosed continuous ink jet printer nozzle assembly defines a flow path having a powered sonic oscillator associated therewith for inputing vibrations to ink flowing in the path, and a cavity for holding closely adjacent but isolated from the ink flow path one or more sensors operable to detect ink vibrations and/or temperatures immediately downstream from the oscillator, whereby such sensed information can be used in feedback controls for changing input power to the oscillator and/or heater/cooler unit upstream of the oscillator, for stabilizing the printed ink pattern. The nozzle assembly further is formed of three subassemblies: an ink driver subassembly having the powered oscillator and sensor(s), and filter and orifice subassemblies respectively adapted to be connected in serial self-aligned sealed orientations to the exterior upstream and downstream sides of the ink driver subassembly, thereby allowing field replacement of the filter and/or orifice subassemblies.