Can I use a different AC adapter with this charger?

No, the input requirements for the Wireless Charger are 5V and 1.8A. (The supplied LG charger is rated as such, and works with the 2013 LG Nexus charger as well.) Many phone chargers only supply about 1.0A. Phones often draw about 600mA to 800mA. In order for the Nexus wireless charger to generate the charging current necessary for a phone, the adapter to power the charger must supply roughly 1.8A.

Take a look at the fine print on all your chargers. Quick tip: a tablet charger (e.g. for a Nexus 7, Nexus 9) may provide sufficient current.