why not just buy a jackery 300 or 500 powerstation and play your normal keyboard and amp into it and play anything anywhere for from $300 to $500 dallars for a pure sine wave setup. I can get 10 hours with my korg pa1000 plus a bose l1 compact amd have power left over.

MEL
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KORG PA1000, KORG PA900, 2 BOSE S1 PROS, 2 BOSE L1 COMPACTS, YAMAHA STAGEPAS 500, ROLAND VP7