This might be MIDI inputs or outputs, alternative connectors like optical audio ... re looking for extremely low latency ...

An S/PDIF optical output is also provided ... The most expensive external sound card we currently recommend is the Sound Blaster AE-9. This model actually sports both internal and external ...

The latest sound card to land on my desk for review ... either be directed to a 3.5mm line out or an optical TOSLink port. Alternatively, the output can be directed to the 3.5mm headphone jack.