Quoted from Nevus:I went with the small adapter. I wasn’t sure I needed the voltage stepper for a lamp.
It's based on the type of transformer. Simply look at the input voltage on the label of your power adaptor. If it says 110-220v, it's an auto-switching power supply and can be adapted with just the plug adaptor. If it doesn't say 110v 60hz, then you need a transformer.