The ES-8 is a USB 2.0 class-compliant audio interface in a Eurorack module, with DC-coupled inputs and outputs that can be used for both CVs and audio. As such it is directly compatible with all popular computer-based CV generation software as well as audio and CV processing iOS apps.
The ES-8 also has ADAT inputs & outputs. This could be used for example to expand the output count via an Expert Sleepers ES-3 and/or ES-6, or to connect a traditional audio interface to add, say, mic preamps or 1/4" line outputs.
An expansion header allows connection of an Expert Sleepers ES-5, to which in turn you can connect our gate, CV and MIDI expanders.
The ES-8 has a high quality internal clock, and it can optionally sync to the clock from the input ADAT signal.