Hi I have purchase a guitar effects rack off eBay and it came without an adapter. It requires 12 volts DC, (sleeve negative, 700 mA). I purchased an adapter from an online electronics retailer, 12 volts 800 mA, along with a 9 volt DC adapter for a midi controller pedal also from eBay. (The midi pedal requires 9 to 12 volts DC, mA unknown, it's not in the manual online either, so I got a 500 mA adapter, I figured that would be enough to power a basic midi pedal). I tested the adapters before I connected them, and the 9 volt adapter outputs 13.02 volts, and the 12 volt adapter outputs 16.54 volts! Are pieces of equipment designed to accommodate this much increase in output from the adapter? Do adapters usually output this much more than they are rated for? Thanks in advance!