get yourself a basic electronics textbook & read up on DC voltage doublers. You can easily build this circuit yourself on vectorboard (or have a knowledgable tech do so for you) mount an input & output connector, assemble this into a bud box, & have enough trigger voltage to do the job. It may be slightly under 12 volts but it should be adequate provided that the processor's 5v output supplies sufficient current.
Or use a ~12VDC wall wart transformer/ power supply, a 5V DIP relay (which will be triggered by your processor's 5V output) the normally open relay contacts then supplying 12V from the P.S. to your amps' trigger input. Mount appropriate connectors & fabricate a trigger voltage cable from this "translator power supply" to the amp. Harder to describe this than to build it - it's very simple.
Or use a ~12VDC wall wart transformer/ power supply, a 5V DIP relay (which will be triggered by your processor's 5V output) the normally open relay contacts then supplying 12V from the P.S. to your amps' trigger input. Mount appropriate connectors & fabricate a trigger voltage cable from this "translator power supply" to the amp. Harder to describe this than to build it - it's very simple.