The sub out board is just a very small digital to analog converter. So yes it outputs in analog only. The current digital output cards can buffer the sub signal in I2S digital format already. If you wanted a digital sub as well as full-range digital out, then just buy two boards with a special adapter cable we could make up for you. The first would be have to have I2S capability, and the second would not, but would have to be external and attached to the back of the Empeg or possibly through spare docking connectors.

Stu