This is a very common question!
This article applies to these units: One iPad/Mac/PC, One for Mac/PC (silver), Duet iPad/Mac/PC and Quartet.
Many customers think because the port on the back of these units looks "non standard" that a standard cable cannot be used. However this is not true in all circumstances.
The port on these units is a variation on USB Mini, which adds two extra leads, the little "humps" on the narrower side. These pass power to charge iPads and iPhones, and also carry some of the iOS Maestro connection data to the Lightning port. Thus if you are using a regular Mac or PC computer these are not in use, so a standard USB Mini cable, like this, will work exactly the same.
You only need the "special" Apogee style port for the Apogee iOS Lightning cable, like this. We build this cable just for these units to work on iOS, so they are proprietary. Thus if you use a regular USB Mini cable, like above, with a Lightning Adapter it won't work, because these leads are needed for that iOS compatibility.
In short summary:
Mac or PC full size computer = Regular USB Mini is good!
iPhone or iPad = Requires proprietary Apogee iOS cable.
If you have any questions please Contact Support.