A medical electrical stimulator provides selective control of stimulation via a combination of two or more electrodes coupled to respective regulated current paths and one or more electrodes coupled to unregulated current paths. Constant current sources may control the current that is sourced or sunk via respective regulated current paths. An unregulated current path may sink or source current to and from an unregulated voltage source that serves as a reference voltage. Unregulated electrodes may function as unregulated anodes to source current from a reference voltage or unregulated cathodes to sink current to a reference voltage.