The ES-3 Mk4 module converts, in a similar manner as the ES-1, control signals from a DAW (e.g. from software like Volta or Silent Way) to control voltages. Unlike the ES-1 it doesn´t use up your audio interface´s analog outputs but it uses the optical output (ADAT Lightpipe). Just connect the ES-3 Mk4 and the audio interface via an optical cable. The connectors of the mk4 version are equipped with multicolor background lightning.