I purchased a 1,500-watt modified sine-wave inverter for my boat, that will easily run my keyboard and amp for hours on end. Of course, the boat batteries consist of 4 T-105 golf cart batteries in a series parallel rig and a 400-ampere hour 12 volt battery. I can run an awful lot of stuff with this much power available.

Gary cool
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)